This is a list of some things with little/no continuity on Glee. If something does get continuity eventually, please remove it from the list.
Please do not add theories as to how something might make sense. Many of these things are "explainable" in some unwritten or extrapolated context. The point of this list is to expose continuity issues, not to say that Glee is terrible, so please do not get defensive.
2011-12 Decorating Budget
In Extraordinary Merry Christmas, Rachel stated that their Christmas decorations had used up the glee club's decorating budget for the entire year, yet they still had Valentine's Day decorations in Heart.
Potential explanation: the students bought their own decorations, or Mr. Schuester used his own money.
Acceptance in New Directions
In The Purple Piano Project, Sugar Motta is denied the entry to New Directions, because she has little musical talent. However, prior to this, Lauren Zizes and Mike Chang had been accepted, despite not being good singers (at that time). In the case of Lauren, they mainly took her because the New Directions were very close to Sectionals and only had 11 members at that point, but this doesn't apply to Mike, as he joined at the beginning of Season 1. However, in Comeback, Lauren sings and is approved by all the rest New Directions and also by Mr. Schue. It was possible that Mike was accepted partly because of his dancing skills, and partly because of Mr. Schue's desire to collect 12 members as soon as possible. Also, in Big Brother, Quinn brings Joe to booty camp and he is accepted in immediately, without auditioning. Also, New Directions has a rejection policy in which no one gets rejected (excluding Sugar), but in The New Rachel they had auditions in which only one got accepted out of many people trying out because of their new found popularity.
Potential explanation: Sugar could have been rejected because she was rude to the Glee Club members, and in The New Rachel they might have been unable to accept more than one person because so many people auditioned.
In Wheels, we find out Artie is sixteen, since he said he was in a car accident when he was 8, and Tina said he's been in his wheelchair for 8 years. This would make him a sophomore at the time. But in The Purple Piano Project, two seasons after that episode, he is a junior, which would make him around 16 or 17.
Possible explanation: none.
Artie's knowledge of Puck's ability to use a calculator
In Saturday Night Glee-ver, Artie doubts that Puck can even use a calculator. It is not likely that he does not know the answer to that since, in Season 2 Artie tutored Puck in Math. And In Season 3 in the episode I Kissed a Girl they where shown to have the same math class.
Possible explanation: it was a snide comment without any actual fact behind it (this also happens a lot with characters like Sue).
In The Sue Sylvester Shuffle, Azimio mentions that it would really mean a lot to his dad if they were to win the Championship game. But in Asian F he claims that he never met his dad and he wasn't brought up by him.
Potential explanation: he might've been referring to his step-dad.
Azimio's Moral Code
In Britney/Brittany, Artie successfully prevents Azimio from attacking Finn because Azimio would have to go through him to get to Finn. Azimio leaves saying, "The only thing saving you right now is my moral code; I don't hit crippled people." In The Sue Sylvester Bowl Shuffle, Azimio is the ring leader of the massive slushie attack on Artie, which Artie tries to talk him out of, but Azimio says he believes in "equal opportunity." This is after Artie is on the football team, cooler than he was prior to joining, so there is less reason to pick on him than before when Artie was just in Glee Club when Azimio couldn't do it because Artie is a cripple.
In Prom-asaurus, Becky was hoping to become queen of the senior prom and seemed to believe that she could run for it. This must have meant that she was a senior in Season Three. However, Becky does not graduate until the episode New Directions in Season Five, which means she can't have been a senior at that point.
Becky's spelling vs. Brittany's
In The Spanish Teacher, Sue tells Becky that she is a better speller than Brittany. However, in Britney 2.0, Becky is shown to misspell her name as "Bocky" on a test, whereas Brittany spells her own name correctly on the same test.
In Original Song, Blaine is referred to as a "Junior Member" of the Warblers. However, in I Am Unicorn, he is said to be a year behind Kurt. Blaine's character was originally said to be a year older than Kurt. However, the term "Junior member" could also mean that he was simply an underclassmen.
Blaine's stance on being "Sexy" for competitions
In Sexy, Blaine seems to be all for being sexy during a competition to please the judges. However, in Hold on to Sixteen, he gets into an argument with Sam that the New Directions shouldn't try to "sell themselves" and be sexy for the judges.
Blaine without hair gel
In Prom-asaurus, Blaine claims that Kurt hasn't seen him without hair gel before. However, in Blame It on the Alcohol during The Rachel Berry House Party Train Wreck Extravaganza, he is seen not wearing hair gel, and in Mash Off, he let his hair go curly during I Can't Go For That/You Make My Dreams. Even Kurt acts as if it was the first time he saw Blaine without hair gel.
Boarding School or Not?
Kurt goes to Dalton, a school in Westerville, which is about two hours away from Lima, Ohio, a long way to drive to school everyday, prompting the assumption that Dalton is a boarding school. However, in The Sue Sylvester Shuffle, he mentioned going to Finn's room every night with a glass of warm milk to start conversation meaning he's living at home. Also in Rumours, Sam mentions that he got a job delivering pizzas at night and saw Kurt when he brought one to Dalton. Assuming this was during a late-night rehearsal for the Warblers, Kurt would probably not want to drive all the way from Westerville to Lima, unless he frequently stays with Blaine or another friend from Dalton, whether it is at their house or dorms, if there are dorms at Dalton. However, there is also the possibility that Dalton has optional room and board. It has been basically confirmed by the frequent commuting from McKinley to Dalton and vice versa that Westerville and Lima have been placed closer together geographically in Glee for the sake of making things simpler.
Brittany's knowledge about pregnancy
In The Power of Madonna, Brittany apologizes to Quinn (because of Quinn's pregnancy) after making an insensitive statement about how nothing bad happens to people who put out, and when Quinn goes into labor, she is seen in the background looking at her stomach and rubbing it; however, in Sexy, she believes babies come from storks.
Brittany and "tough love"
In Comeback, when Rachel is angry at Brittany for taking all the credit for her trending outfits, Brittany tells Rachel "I'm going to give you some tough love right now" and tells her off. However, in Britney 2.0, she seems to have never heard of the term "tough love" and even says "tough love feels a lot like mean."
Brittany and My Headband
In Blame It on the Alcohol, Rachel sings My Headband to Finn with nobody else around. However, in Original Song, Brittany claims that it is her favorite song, yet she is never shown hearing it. It is possible that Rachel performed it for members other than Finn.
Burt's knowledge of Kurt's sexuality
In Preggers when Kurt comes out to Burt, he claims that he had known that Kurt was gay since he was 3 because all he wanted for his birthday was "a pair of sensible heels." However, in Goodbye, Burt says that Kurt started becoming more feminine and flamboyant around age 7 or 8 after his mom died.
Explanation: 3 year old Kurt asked for heals but after his mom died he started going even more flamboyant at about age 8.
Coach Beiste's broken foot
In Asian F, Coach Beiste comes to school with a broken foot and crutches because she kicked a fire hydrant when she learned Ace Of Cakes was cancelled. However, when she appears 2 episodes later in The First Time, she is not wearing a foot cast or using crutches. A broken foot takes at least 6 weeks to heal. Now while The First Time was aired a month after Asian F, in Glee, 6 weeks were not likely to have passed since it was 2 episodes after Asian F. But they did prepare the whole musical between Asian F and The First Time, so it's not impossible for a month a half to have passed between the episodes
Dalton Academy's zero-tolerance harassment policy
In Season 2, it is established that Dalton Academy had a zero-tolerance policy for bullying which Kurt says in Furt that it's regularly enforced. However, when Sebastian is reported to the Dalton headmaster both times, they do absolutely nothing about it, as Blaine mentions in On My Way. However this incident did not take place during school hours or involving only Dalton students. Such incidents may not be covered in the policy.
In Mash-Up, when David Karofsky makes his first appearance, he is introduced as a hockey player and is nowhere to be seen during the scenes with the football team. In later episodes, however, he is a football player just like Finn, Puck and Mike.
The Troubletones have 7 members: Mercedes, Brittany, Santana, Sugar and three extra girls. If nobody joins New Directions, how did Shelby get 3 extras in her group? The same can apply to West Side Story; who played all the Shark Girls? However, there are probably theatre and regular choir students who auditioned for the musical, and also the Troubletones. Also, since the three backups in the Troubletones are cheerleaders, and Santana is their captain, she might have recruited them. These extra three Troubletones are not seen or heard from again after Nationals, and it is not explained whether they have graduated or chosen not to join the glee club for the following year, despite having just won a national championship. In season 1, Sandy had previously run the Glee club. A few seasons later, he mentions that Vocal Adrenalines weakness is that they can't do a funk number, suggesting that their Glee club had gone up against them, or performed in competetions. Glee clubs need 12 members, and when Will takes over, none of the people from the previous club except Rachel join.
In The Role You Were Born To Play, Glease and I Do Sue says Finn is 19. In The Quarterback, the memorial plaque says "Finn Hudson: 1994-2013." The Role You Were Born To Play and Glease take place in 2012, meaning if Finn was 19 at that time, he would have been born in 1993. It is possible that Sue just assumed Finn was 19 because people in their first year after high school usually turn 19 at some point that year.
In The Break-Up, Finn tells the New Directions that he auditioned for glee-club with a song from Grease, although he didn't. He didn't even have an audition, since he was black-mailed into joining New Directions. You're the One That I Want is a song from Grease that was sung by Finn in the Pilot, but it wasn't his audition song.
Finn's job in Wheels
In Wheels, Finn wants to help raise money for Quinn's sonogram, so Rachel helps him get a job by urging a company to hire him while he is pretending to be in a wheelchair. While it is never mentioned what kind of job it was, it was also never mentioned how long he kept that job, as he was never shown to have been fired from it or quit.
Finn singing after Nationals
In The Break-Up, Finn claims that he didn't sing after Nationals, which is untrue. He sang Roots Before Branches and You Get What You Give in Goodbye. We Are the Champions technically was after Nationals, too.
Finn wanting to leave Ohio
In New York, Rachel mentions how Finn is "Too much of a country boy" to want to live in New York with her. Also in I Am Unicorn, he talks about working in Burt's auto shop and says "Would that be so bad?" However, in The First Time, he is upset about not getting picked by Cooter Menkins, who chooses Shane instead and he yells and cries because he is upset about being stuck in Lima forever. It makes no sense how at one time he appears to like living in Lima, then soon after he seems to be upset about having to stay there. Maybe because everyone has decided where they're heading and what they want, like Rachel being determined to go to NYADA, he realized he wanted bigger things for himself too, which is why he was so upset.
In Funk, the episode centers around Vocal Adrenaline psyching out New Directions, and New Directions fighting back by performing funk numbers. At the beginning of the episode, it is stressed that Vocal Adrenaline has never pulled off a funk number before; however, they sang Another One Bites the Dust at the start of the episode, which is a funk rock song, meaning it infuses elements of both funk and rock music. Also, Quinn sings It's a Man's Man's Man's World for the funk assignment, which is not a funk song, despite being originally by funk artist James Brown. Also, in the episode, Mercedes claims that when white people do funk you end up with "KC and the Sunshine Band." Harry "KC" Wayne Casey is the only white member of the group; their past bassist/drummer Richard Finch was white as well, but the majority of the group is not white.
Glee Club's Popularity
In A Night of Neglect, no one in Glee was able to invite people to come to the benefits despite the fact that they have popular characters. This conflicts with several scenes shown previously in the series. New Directions had a full house for their fall invitational in The Rhodes Not Taken, and yet they can only scrounge up six audience members in A Night of Neglect, the majority of which are hecklers commanded by Sue. In Born This Way, when Kurt and New Directions members sang Barbra Streisand, they have plenty of flashmobbers willing to help Rachel feel more confident with her looks. Also, in A Very Glee Christmas, the students heckle the Glee club and the teacher even throws her shoe at them, and in The Purple Piano Project, the students start a food fight after they sing We Got the Beat. In Heart, when The God Squad sings Stereo Hearts to Rachel, all the students seem very into the song and they all stand up and cheer. On the other hand, when the New Directions perform Empire State of Mind, the McKinley students act completely indifferent and do not care, with the exception of Sam and Sunshine. In addition, there is always an uproar of cheering at the end of all the assemblies in which New Directions has performed.
In Season 1, Jesse understands all of the vocabulary that Rachel uses and properly uses complex words such as "fastidiously" in sentences. When he returns in Prom Queen, Jesse claims that he didn't know you have to take all your classes in college and doesn't know what a recession is, suggesting that he isn't that smart.
Kitty on Forced Vomiting
In Glease, she constantly psychs Marley about her weight gain. She altered the size of the costume and made comments about Marley being fat. She, then, advised Marley to force vomiting. Marley asked her if she does it and Kitty replied that she will if she has a fat gene. However in Dynamic Duets, Kitty asks Marley if she still force vomits and Marley said she's been doing it for a week now. Kitty said that the reason that they might be getting along is that they seem to have a lot in common. She, then, tells Marley that she does it all the time to keep her trimmed figure retained.
Kurt's curiosity about sex
In Blame It on the Alcohol, when Burt gets angry with Kurt because Blaine slept over, after Kurt apologizes he says "But maybe you could step outside your comfort zone and educate yourself, so that if I have any questions I could go to my dad like any straight son could." However, when Burt wants to have "the talk" with Kurt in Sexy, Kurt protests and shoves his fingers in his ears and starts singing loudly.
Kurt's view on men dressing like women
In Saturday Night Glee-ver, Kurt tries to convince Unique not to dress as Unique and claims that while he has worn some flamboyant outfits, he has never dressed like a woman. Kurt also refuses to dress up as a woman for the New Directions' Nationals performance (Props). However, in Acafellas, Rachel reports that she saw Kurt wearing a corset to one of his classes. In Audition, he also states to Mercedes that 'fashion has no gender'.
Lauren's original crush on Puck
In Special Education, Lauren finds Puck in a port-o-potty, and he asks her to join Glee club which she agrees to do if he gives her seven minutes in heaven. Then in A Very Glee Christmas, she tells Santa Claus, "I want Puckerman to love me. He's a fox!" However, in Silly Love Songs, she is suddenly playing "hard-to-get" with him, and it is revealed that he no longer turns her on after only 3 minutes of the 7 he promised her. She even threatens him for staring at her which makes no sense because if she's no longer into him, she wouldn't have asked Santa Claus for him to like her.
In Born This Way, Lauren digs up the dirt on Quinn, eventually finding out about her past life as Lucy Q. Fabray. When Quinn states that people at her old school made up a nickname for her, Lauren suggests "Juicy Lucy," and Quinn admits "Lucy Caboosey." Shortly after, we find out that Lauren had made some posters with "Vote For Lucy Caboosey" on them, meaning they were created before Lauren knew the nickname. However, it may be possible that Lauren simply wanted Quinn to admit she was called "Lucy Caboosey."
Marley's body issues and eating disorder
In Glease, Kitty convinces Marley that she's fat by altering the size of her costumes so they wouldn't fit her, and then suggests Marley to become a bulimic, which Marley does. However, in Dynamic Duets she wore a spandex outfit, in both competitions she took part in (in Thanksgiving and All or Nothing) and the "Tell Him" performance from Sadie Hawkins, she wore short dresses, and in Guilty Pleasures she wore a short, tight dress as Posh Spice, all of which a bulimic would not agree to wear, at least not without feeling a lot of pressure, which is only shown in two of these examples. Also, it is implied that she has been attending a doctor to get over her disorders since Glee, Actually, but it is known that they haven't gone at least until Sweet Dreams, a month after that.
McKinley's P.E. program
In Dream On, Sue tells Bryan Ryan that "When daily P.E. was cut at this school, no one batted an eye." However, in Season 3, certain episodes show the Glee kids in WMHS P.E. uniforms. However, Sue only said daily P.E. was cut, not that they had no P.E. at all.
McKinley's Violence Policy
In I Kissed a Girl, Santana is about to get suspended for slapping Finn in the face. Figgins justifies that move with a zero tolerance policy that the school has had on violence since an incident three years before. However, this policy clearly didn't exist in the previous Seasons, because there had been cases of violence before where nobody got punished at all. For example, Puck and Finn brawled with each other in Wheels and Sectionals, as did Finn and Sam once, but they got away with it. Karofsky had violently shoved Kurt into a locker several times and most likely had beaten up several other students prior to that, yet Sue then claimed she had no reason to expel him. Santana herself has been in several fights, with Mercedes, Quinn, and Lauren, and she even made Rory's nose bleed in the same episode, however, she was never called to account for that.
McKinley High's lunchroom
In Seasons 1 and 2, the cafeteria is average sized. However, in The Purple Piano Project, it is noticeably larger with a raised ceiling and striped-colored brick walls that were not there before. Then suddenly in Asian F when Mercedes is sitting with Shane, the lunchroom is back to normal. While one may think that in high school, there are often 2 cafeterias: one for lower-classmen, and one for upperclassmen, the New Directions have been seen sitting in both. In a normal high school, teachers would probably not allow students to switch cafeterias whenever they feel like it. And even if the larger one where We Got the Beat took place was just another part of the cafeteria, it has not been shown at any other time throughout the series. However, we know that Glee was filmed at an actual high school, so we may be able to assume it is always there, they just aren't usually there.
In Home, Quinn comforts Mercedes when she is struggling to be thin and is very nice and uplifting and tells her that it's okay to be comfortable in her own body. In Funk Mercedes even invited Quinn to move in with her and when Quinn was in labor, she explicitly asked for Mercedes to be present when Beth was born. Ever since, they have not been seen communicating very much, if at all. Mr. Schuester states that Quinn hasn't even said thank you to Mercedes for letting her live in her house.
In only one performance (one song from Sectionals and Regionals from season two) are they ever seen using microphones. How they project their voice to over 1000 people and over clapping is very strange, though they used mics when they performed Valerie, Get It Right, and Loser Like Me. However, on Broadway, hidden and drop down microphones are used to project the actors voices when speaking and singing; these could very well be used.
Explanation: In season two where they compete at Regionals Rachel sings her ballad into a microphone but it shows someone coming onto the stage and handing her one that goes over her head while taking the stand up one off of the stage.
In Prom Queen, when Artie sings Isn't She Lovely to Brittany, Ms. Hagberg is portrayed as the Home Economics teacher. However, in I Am Unicorn she is teaching Geography (where Brittany says that the capital of Ohio is "O") and in I Kissed A Girl she is shown teaching Math. She is seen as a history teacher in The Spanish Teacher. It is possible that she has taken the same role that Holly and Shelby had/have taken as a multi-subject substitute.
Nationals Top 10 and Showcase
In New York, it is stated by Rachel that at Nationals, the top 50 show choirs in the nation compete for the top 10, then move on to Showcase the next day to compete for the National title. However, in Nationals, the choirs are narrowed down to the top 3 immediately after performing, and no top 10 list is made.
New Directions' Budget Cuts (As Of Season Two)
In season two, Will claims that Coach Beiste's new football budget had siphoned off 10% of the glee budget and had cut all of the show choir's transportation to and from events; however, New Directions has no problem getting to sectionals in Special Education. No explanation for how they were able to pay was made, and no attempts at any fundraising for the club are made until Finn sets up his kissing booth in Silly Love Songs (which is already after one competition). In addition to that, in several episodes, New Directions have not been able to do certain things, such as pay for a bus to competitions, because they have not had enough funds to pay for them; however, they still manage to buy different sets for almost every episode that would normally cost a lot of money, something that New Directions do not have if they can't even pay three hundred dollars to rent a bus. For example, the light screen in the background in The Substitute when Rachel and Holly are performing Nowadays/Hot Honey Rag from Chicago.
New Directions Boys' insecurities about singing Lady Gaga
In Theatricality, Finn complains to Mr. Schue that he and the other guys (with the exception of Kurt) don't want to do Lady Gaga because her music is too girly. However, in Born This Way, they do not object when Mr. Schue tells them that they are singing Born This Way. It is possible however, that the boys do not object to Gaga when they don't have to wear the Gaga-esque costumes.
New Directions singing a "Funk" number to beat Vocal Adrenaline
In Funk, Will finds out from Sandy Ryerson that Vocal Adrenaline has a weakness, which is Funk music. When Give up the Funk was performed at the end of the episode, Jesse and the rest of VA are petrified and refer to themselves as "soulless automatons" because they could never pull off a Funk number. However, New Directions performs a Journey medley instead of a Funk number at Regionals. They also seem scared stiff after learning that Sue is a judge. Now which while it makes sense to be scared that Sue will crush them at Regionals, it makes no sense that New Directions is excited and confident about their new style of music and Puck even said to Vocal Adrenaline quite confidently "See you punks at Regionals!" and suddenly in the very next episode they all believe they are going to lose. However, this particular error could probably be explained by the fact that Funk was originally supposed to air before Theatricality, but was changed at the last minute. Notice when you watch Funk before Theatricality, it makes it seem like Vocal Adrenaline is doing Lady Gaga music to beat New Directions and their Funk music.
Figgins' List of Approved Songs
In Showmance, Principal Figgins tells Will that New Directions can only perform songs from a list of approved songs that all have Jesus or balloons in the title. However, after Quinn's performance of I Say a Little Prayer, the list is ignored without any punishment or further mention. In addition, in Grilled Cheesus, when New Directions tries to sing songs about religion, Figgins tells them that they can't.
Puck's Geography Exam
In Choke, Puck studies for and takes a European geography exam. However, after he fails, Coach Beiste helps him study to retake it, and quizzes him on the countries of South America, not Europe.
Puck's stance on appearing "gay"
In The Sue Sylvester Shuffle, Puck reprimands the football team because they are afraid of being called "losers" or "gay," implying that he doesn't care that people think he is gay just because he is in Glee club. However, in The Spanish Teacher, he admits that he stopped washing himself "down there" because it "seemed kind of gay," and in Saturday Night Glee-ver, he tells Finn that "2 dudes in one bed is like CONFIRMED gay."
In Dream On, Puck writes down that his biggest dream is to have a threesome, implying he has not done so prior. However, in Britney 2.0, he reveals to Jake that his first threesome was at age 7.
In Audition, Puck admits to Jacob Ben Israel that he spent all his summer pool-cleaning money to get a vasectomy, claiming it was "the responsible thing to do" after Beth was born. However in The First Time, Puck says to Finn that he doesn't use condoms, and it works for him 99% of the time. In I Kissed a Girl, when Puck and Quinn are about to have sex, Puck says to Quinn "I didn't bring protection" assuming that he can still get her pregnant. While one may argue that vasectomies can be reversed, Puck has never mentioned getting it reversed.
Quantity of Kurt solos
In Dance With Somebody, Kurt claims during an argument with Blaine that he used to get solos every week before Blaine transferred to McKinley, which, however, is untrue according to Kurt in Season One, where he joined the Cheerios because he thought he wasn't getting enough solos. Since he spent half of the school year at Dalton Academy in Season Two, it also seems unlikely that he had been talking about that time.
Quinn's big plans for New York
At the end of Funeral, just after Finn broke up with Quinn, Quinn tells Finn that she planned for something in New York. However, in New York, she does not go through with any plans. Instead, she blows up at Brittany and Santana, who calm her down and comfort her by helping her to go get a haircut.
Quinn's Due Date
In Hairography Kendra tells Terri that the baby is due around spring break; however, Rachel tells Finn in Laryngitis that Jesse is on Spring Break. Journey is five episodes later which must be around a month or two, and even so, in Journey, Quinn says her due date is a month after Regionals; therefore, according to Quinn she delivered a month early, and according to Terri, she delivered a month or two late.
Quinn's on/off pursuit to get Beth back
From I Am Unicorn to Mash Off, Quinn actively tries to make Shelby look like an unfit mother while trying to be friendly to her at the same time, which is thwarted when Shelby finds out. Then in I Kissed a Girl, she admits to Puck "trying to get Beth back was a stupid idea" when she tries to seduce him. However, when Puck tells her that he slept with Shelby, she suddenly wants Beth back until the end of Hold on to Sixteen when she is finally convinced by Sam, Rachel, and Shelby that what she wants to do is wrong.
Quinn's train ticket
In Goodbye, Quinn buys herself a train ticket to see Rachel, as well as a ticket for Rachel to visit her in New Haven. However, in Thanksgiving, Quinn tells the other alumni that Rachel had complained to her via email that Quinn hadn't used the ticket that Rachel bought her, which is an error since Quinn is clearly the one who bought herself the ticket.
Rachel mentions that she was born on December 18, 1994, which would make her 14-15 in Season One when she was a Sophomore. However, Sophomores are usually aged 15–16, unless she skipped a grade, and she mentioned to Jacob Ben Israel in her interview in The Rhodes Not Taken that she had been performing for sixteen years.
In Hairography, her bathroom door is opposite her bed, and also seen in Bad Reputation, the outside door is on the right wall. There is no sign of a window. In The Power of Madonna, the outside door is on the left, the bathroom door is on the right, she gets ready for 'doing the deed' in there. In Dream On she comes out of it combing her hair and there's a window behind her desk, opposite her bed. In Mash-Up, she also has different room positions, such as where her desk is.
Rachel's Dance Skills
In Pilot, Rachel's flashback showed her taking ballet, tap dancing and other dance classes due to her parents' insisting her to do so. She's even taken some ballet lessons with Jesse (as said in Bad Reputation) even performing Total Eclipse of the Heart while in those classes. You'd think that Rachel's dancing would be exceptional with all those lessons, but in The New Rachel, Cassandra insults her dancing saying that she "sucks." However, lessons does not make one to the level of a broadway dancer, and it was stated later in Season 4, that Cassandra was just trying to push Rachel to be her best.
In The Rhodes Not Taken, Rachel is seen having pepperoni pizza with Finn, even remarking that it is good pizza, although she could possibly have said this to impress Finn, and not seem like a spoilsport. She is also noted as cooking venison in Ballad. However, in Funk, Giselle from Vocal Adrenaline points out that Rachel is a vegan after the group eggs her; and Rachel claims to have had nightmares about the baby chicks' mothers coming after her for revenge after Jesse St. James and the other members of Vocal Adrenaline's assault. However it is possible that she changed her eating habits since the series started. In Laryngitis, Rachel eats a bowl of cereal which possibly has milk in it. Later, in Michael, she brings Blaine chicken noodle soup. Also in Heart, when the Hudson-Hummels go to the Berry's house for dinner, they eat duck, and in Choke, she claims that she doesn't drink milk before performing because it causes phlegm, implying that she drinks milk, which isn't vegan. She is also seen cooking duck for Brody in Makeover, and after she messes the duck up orders a pizza to eat with him. In The Break-Up, Kurt offers to make her a croque madame, which contains both cheese and egg, and shortly afterwards, she cooks an egg for Finn. Then in Thanksgiving, she states that she is a vegetarian, not a vegan.
Rachel's extra-curricular activities and NYADA
In Mattress, Rachel reveals that she is part of just about every single club at McKinley High. However, in The Purple Piano Project, she claims that like Kurt, she is thin on extra-curricular activities and picks up the idea of putting on West Side Story. In Asian F, she runs against Kurt and Brittany for class president because she feels she has not been involved in enough activities to secure herself a spot for NYADA. If Rachel really was involved in all those clubs she mentioned in Mattress, she would not have needed to run for class president. Also, Shelby even read Rachel's resume in Mash Off and says "I feel sorry for the people who don't have these big ticket items on THEIR resume." However, it could just be that Rachel is so worried that she sees what she has already done as not enough, and she feels like she always needs more to go on her CV. Also, in Props, when Rachel is telling Tina that she deserves the solo for Nationals, she also tells her that she is involved in over seventeen extra curricular activities.
Rachel's on/off views and knowledge of premarital sex vs. celibacy/West Side Story
In Showmance, Rachel calls out the entire celibacy club and explains that "it's been proven that celibacy doesn't work in high schools" and also says "Girls want sex just as much as guys do." However, in The Power of Madonna, she feels insecure both times when she and Jesse attempt to have sex and feels like she's not ready. She also says that she won't be ready to have sex until she is 25 in Grilled Cheesus and chooses to remain celibate in Sexy in order to focus on her songwriting for Regionals. However, in The First Time, Artie has convinced her that she needs to have sex in order to give an authentic performance, so she hastily and unsuccessfully tries to have sex with Finn before opening night. Since Rachel, who is a Broadway EXPERT, actually said in Preggers that Maria is one of her dream roles, implying that Maria is the perfect role for her, she should not have needed to listen to Artie or even believe him that the role of Maria is about "sexual awakening." She also does not seem to have considered the consequences of having premarital sex in high school (Pregnancy, STDs, etc.), which could possibly kill her chances of ever being on Broadway.
In Saturday Night Glee-ver, Rachel tweets a message for Finn to read, but in Props, she says to Tina that she doesn't have a Twitter account. It is however possible that she had deactivated her account prior to Props due to her practices for NYADA and Nationals.
Rory's Valentine's Day-Sponsor
In Extraordinary Merry Christmas, Rory asks Sam if he would like to be his Valentine's Day-Sponsor as well, since he was such a good Christmas-sponsor, to which Sam agrees. However, in the Valentine's Day episode, Rory is seen pursuing Sugar all by himself, without Sam's help.
Explanation: When Sam found out Rory was going to try to get Sugar when he knew Artie was interested he ditched Rory and decided not to help. It's pretty clear by the fact when Artie sings to Sugar all guys back him up who are there.
Ryder quitting and rejoining the New Directions
In Season Two, Quinn and Santana wanted Sam to run for prom-royalty with them at junior-prom, which must have ment he was a junior in that Season. However, since Sam doesn't graduate at the end of Season Three, he must be a junior again that year.
Sam's feelings about being a stripper
In Hold on to Sixteen Sam claims that he's ashamed about having to work as a stripper. But in Makeover, when being asked if he isn't ashamed of being a stripper, he claims not to be. However the second statement may be a lie for the sake of his campaign.
Sam's feelings for Brittany and Santana's knowledge of them
In Swan Song, Sam Evans claims that he has had feelings for Brittany Pierce for years and that Santana Lopez was mean to him because she knew of those feelings. This does not match what has really happened. Santana never showed any true jealousy towards Sam. She used to be hostile to him, but Santana acts hostile to almost everybody she interacts with. There is nothing to indicate she acted hostile towards him because of jealousy.
Sam's writing hand
Sam claims to be left-handed in 100, but he has been exclusively seen writing with his right hand on the show.
Senior Ditch Day
In Big Brother, the seniors of New Directions have their Senior Ditch Day. However, Tina and Rory were there and neither one of them are seniors. While Sugar's classification is unknown, Tina and Rory should not have been able to skip. Artie was also mentioned to be a junior in The Purple Piano Project and he should not have been able to skip school to take Quinn to "Life Rolls On." Since one may argue that it's just a New Directions Ditch Day, there's really no point in calling it Senior Ditch Day since not everyone who skipped were seniors.
Shelby's unexplained disappearance from McKinley
Shelby has not been seen or heard from, or even mentioned since Hold on to Sixteen after the Troubletones disbanded. Although she DID say "I might as well enjoy my last night as a teacher" (which she only said because Quinn was going to try to get her fired), it was never properly addressed whether or not she left McKinley. However, in Sweet Dreams, it is revealed she is currently living in New York with Beth and is running a Broadway daycare center, where Broadway actors and actresses will drop off their kids and Shelby watches over them, as well as playing theatre games with them.
Shelby giving Rachel away
In Season 1, Shelby talks about how she was a surrogate mother for Rachel's gay dads. However, in I Am Unicorn, she says that she gave Rachel up for adoption, but it wasn't necessarily an adoption since it's said in Pilot that one of the Berrys is Rachel's real biological father. If that is so, then it wasn't an adoption, it was a surrogate pregnancy.
Special Education at McKinley
In Showmance, Sue gave Will a list of Special Ed classes so he could find recruits for Glee club. In Season Three, while Sue is running for congress, she states that there were no Special Education classes in McKinley.
In Funk, when Will comes to visit Sue at her house, he is literally tripping over the number of trophies in the hallways and then in Sue's bedroom. When he and Emma re-visit the house in Comeback, the number of trophies has radically decreased. They were possibly moved.
Sue's Short Hair
It can be remembered that Sue revealed to Mercedes and Kurt in The Power of Madonna that she was jealous of Will's hair and that she was forced to wear hers short because she and her sister Jean bleached it when she was six with ammonia and other cleaning products. But in Puppet Master, she said that she cut her hair short to look more strict. This was a decision she made solely on her own and something she decided to do not forced to. So above other things, she had long hair growing up and only wore her hair short when she started teaching.
Sue's thoughts about pregnancy
In Vitamin D, Sue states that she doesn't know why one would even want a child because the desire to procreate shows "great personal weakness," and she also says "Don't have the time; don't have the uterus." However, in The Spanish Teacher, she suddenly wants a child, and subsequently gets pregnant with and gives birth to Robin Sylvester. It's not impossible, however, for her to have changed her mind - especially after the death of her sister and the love she felt for Becky. It's also fairly apparent through much of the series that Sue just says ridiculous things, and no comment is ever made to whether or not most of what she says is true.
The "Something special" scene
In Pilot, when Will tries to talk to Rachel about rejoining glee-club, she says, "Being a part of something special makes you special, right?". Tina wasn't in this scene. However, in Journey when the New Directions go to Will's house for dinner, Tina starts crying and says, "Rachel was right. Being a part of something special, it made me special." However, this could have been a common saying of Rachel's, since she says it again in Tina in the Sky with Diamonds.
The "Too Young To Be Bitter" Club
The Too Young To Be Bitter Club was disbanded after the success of the Sadie Hawkins dance in Sadie Hawkins, but in Love Love Love Blaine mentions that he saw Tina attend a meeting alone (eating all the food, that is meant for members) meaning the club was never disbanded.
The April Rhodes Civic Pavilion
In Home, April Rhodes buys William McKinley's auditorium due to an incident where Sue Sylvester booked it for a longer duration leaving the New Directions without a place to perform. April then left it to the club in order to guarantee they always had an auditorium they could resort to. In Glease, however, Sue announces that she has booked the auditorium for two weeks again, although that is what April Rhodes had tried to prevent.
The Berrys and takeout vs. cooking
In Wheels, Rachel states "My family is fully committed to takeout." However, Hiram and Leroy cook dinner for the Hudson-Hummels in Heart. Also, it is mentioned in Ballad that Rachel is a 'great cook' and appears to be cooking venison, something relatively culinarily advanced. Finally, Rachel is continually shown baking, such as the 'I'm Sorry' cookies she baked Mr. Schuester in Acafellas and the banana bread she baked for Finn in or prior to Britney/Brittany.
In Born This Way, Karofsky and Santana start a club called the Bullywhips as a way to stop bullying and provide a safer school environment for all students, like Kurt whom they successfully get to come back to McKinley. However, after Prom Queen, they are not seen or heard from and in The Purple Piano Project, Finn gets slushied by the hockey team, and they also shove Rory into a locker in Pot o' Gold, both of which should have been prevented by the Bullywhips. And even if the club was "disbanded," there is no way Figgins would have let them stop patrolling the hallway, if he is even a good principal. However, this could probably be explained by the fact that Karofsky transferred schools, as mentioned in The First Time.
The Cheerios consecutive National championships
In Season One, it is acknowledged that Sue had won five consecutive National championships, then she wins her sixth one in Funk. However, in Journey, the announcer at Regionals says that Sue is "fresh off her fifth consecutive National championship, and in Audition, Figgins says to Sue "I'm sure you can manage a sixth consecutive National championship without two confetti cannons" implying that Sue has only won five championships, not six. Then in The Sue Sylvester Shuffle, it is said once again that she has only won six, and that she lost what would have been a seventh consecutive National championship.
The MVP Award
In Original Song, Will awards Rachel with the new MVP Award, which would be awarded to the most valuable member after every competition. She most likely got it from writing an entire original song on her own, Get It Right, and helping them succeed. The award isn't continued nor mentioned at Nationals in New York, which may be due to time restraints and several scenes being cut. However, in Hold on to Sixteen and On My Way, an absence of the award occurs, and in Nationals the award is given to Unique by the judges, not by Will.
The New Directions' Costume Committee
In Pilot, Mercedes is assigned by Finn to take care of the costumes. However, since the end of that episode, the costume committee hasn't been heard from or seen until Props, where it is revealed that Tina, Sugar, Joe, and Rory are assigned to it by Mr. Schuester. However, Finn was not in a place to assign permanent roles to member of the Glee Club, and 3 years had passed in between the 2 episodes.
The Promise Ring
In Furt, Sam tells Quinn that he loves and would like to marry her in the future, then gives her a promise ring; however, when they broke up in Comeback, the ring nor promise was mentioned, and it is never shown what happened to the ring.
The Reason Emma has OCD
In Showmance, Emma says that she got OCD when her brother pushed her into a pond at a dairy farm. In Asian F, it is revealed that she got OCD because she grew up watching her parents clean their cups at restaurant. It could be that she has OCD for a buildup of different reasons. In Asian F, you can see by what her parents are like she had the kind of childhood that could cause her to get OCD.
The Rosedale Mennonites
The New Directions compete against The Warblers and another amish band at Sectionals in Season Four. Two teams end up being disqualified, namely the New Directions in Swan Song, and The Warblers in Naked. This should make the Rosedale Mennonites the winner, since they were the only team to not have been disqualified. However, after the Warblers get disqualified, the New Directions, who had previously lost due to an offence to the rules, are made the victors.
The School Paper ("The Muckraker")
In Showmance, when Quinn, Brittany, and Santana try out for New Directions, Quinn tells Will "I'm pretty sure you've read about this in the school paper: Finn and I have been an item for a while now." And in the the Rhodes Not Taken, Rachel was being interviewed by Jacob thinking it was for the school newspaper. However, in Rumours, Sue tells Terri that she wants to bring back The Muckraker, to which Terri responds, "But the school newspaper was discontinued two years ago due to a lack of interest" meaning that the Muckraker would have been discontinued long before Finn and Quinn were an item. The Muckraker is once again mentioned in Glease, when Kitty mentions that Fletcher Mantini, a theatre critic from the school newspaper, is in the audience, and later on, gives their performance of Grease a good review. This imply's that The Muckraker is still active.
The Teachers' Lounge
In Bad Reputation, you notice a long corridor next to where the Teacher's lounge is located. However, in A Very Glee Christmas when the New Directions sing Welcome Christmas, that corridor outside the teachers' lounge is gone and a staircase is there instead.
The Troubletones members
In Asian F, Shelby Corcoran explains how she is having problems recruit girls for The Troubletones. However, by the time they perform Candyman the club already has seven members, and even twelve when they compete at Sectionals, which seems weird, since the New Directions had only gotten Sugar Motta to audition when they tried to campaign for new members in The Purple Piano Project. At the same time, the New Directions had trouble recruiting the just about three extra members that they needed to be able to compete, even though Shelby Corcoran had admitted, that if a kid at school wanted to sing in a glee-club, they would rather choose the New Directions.
The vest Mr. Schue wore when he first met Emma
In Funeral when Will and Emma are going through his vests, she picks up a bluish-gray patterned vest and he tells her "I wore that the first time I met you." However, in Yes/No, we see a flashback of the moment they met and Will is wearing a brown vest.
The Warblers Council
In Special Education, it is said that the Warblers elect 3 upperclassmen to lead the Warblers. However, in Michael, Sebastian takes over the Warblers and becomes captain of them. Now while it is likely that Dalton considers juniors upperclassmen since Thad was on the council in Season 2, Sebastian says during his introduction scene in The First Time that he is a freshman. It is also highly unlikely that they would have let him take over the Warblers the way he did, especially since he just used them to help him bully the members of the New Directions.
Tina dumping Artie and Mike
In Love Love Love, Blaine is concerned about Tina because he says she'd been dumped by both Artie and Mike in the past. However, Tina was the one that dumped them, as she was shown to have dumped Artie over the summer for Mike in Audition, and dumped Mike before The New Rachel, and was even said to have dumped him shortly after getting a tattoo of his name. In addition, it is mentioned by Kitty in Love Love Love that Tina dumped Artie.
Troubletones in I Kissed a Girl
In I Kissed a Girl, the New Directions and The Troubletones are notably seen together throughout the episode. However, the 3 extra girls are nowhere to be seen during meetings and the performance of I Kissed a Girl.
In Saturday Night Glee-ver, when Unique is telling Mercedes and Kurt how horrible Jesse is, she says that Jesse is "nothing compared to the kids at school, or [her] parents" which makes it seem like her parents are highly unaccepting. However, in Glease, they seem to support her enough to want to move to a more liberal city where she can openly be herself, like Chicago. In Thanksgiving, she says that her parents want to send her to a camp for "little boys who like to wear dresses." It is possible that they may have been putting on an act for Figgins.
Use of performance enhancers
In Sadie Hawkins, according to the rules about show-choir competition, using performance enhancing substances is forbidden during a competition. However, in Hell-O, it is stated by Tina that the members of Vocal Adrenaline take human growth hormone. Since the New Directions knew about this, it can't have been a well kept secret. Vocal Adrenaline has never been disqualified from a competition, yet the Warblers get disqualified in Naked.
Vocal Adrenaline/Jesse St. James
It has been stated that in season one, that Jesse St. James had been lead singer of Vocal Adrenaline for four years. Yet, he is nowhere to be seen in any number performed by Vocal Adrenaline prior to Hell-O, where he makes his first appearance.
Will's knowledge of Terri seeing a therapist
In Sectionals, Terri tells Will that she is seeing a therapist at the local community center. However, in The Substitute, Terri mentions that her therapist says that she "likes Will best when he's weak" to which Will asks inquiringly "You're seeing a therapist?" However, it's possible that Will forgot that she told him about it.
Will's relationship with Terri in high school
In Pilot, Will mentions that in high school, Terri used to be "filled with so much joy," and in Dream On, he says that they grew apart after they got married. However, in Blame It on the Alcohol, he tells Coach Beiste that when he was in high school he consumed a lot of alcohol just to "deal with Terri." If Terri really was the way Will described her in high school, he more than likely wouldn't have had to drink to deal with her.