* ActorAllusion: Mr. Gilbert, the imposing sadist who openly hates the students and even admits that the sole reason most people become teachers is because they stopped doing background checks, is played by comedian Greg Davies who was a teacher for thirteen years.
** Jay's dad claims that Neil's dad [[Series/TheITCrowd looks like a vicar.]]
* DawsonCasting: All four lead characters' actors were, at the youngest, 21 at the time of filming the first series. This means that, if they had left college/sixth form and gone straight to University, they would have graduated from that three years ago. This is one of the few positive examples of the trope, because all four of them [[OlderThanTheyLook sure don't look like they're in their mid-20's]].
** Well, there is the scene where Will is in bed with Charlotte. No average-sized 16 year old has that much chest hair...
** Inverted, however, by most extras being Year 7 students- and not due to begin sixth form for another five years.
** The best example: Susie, one of the "freaks" who joins the Sixth Form with Will, is said to be taking her A-levels four years early, making her either twelve or thirteen. The actress playing her was seventeen and actually would have been taking her A-levels.
** There's also Simon's brother in Series 3, [[SheIsAllGrownUp who has quite visibly aged.]]
** The age disparity increases with the [[Film/TheInbetweeners2 second film]] as the gap betweeen the release of the two films is three years, but InUniverse only a few months has passed. Making Simon Bird and Joe Thomas roughly a full decade older than their characters.
* EnforcedMethodActing: None of the actors who played the audience during the fashion show episode (including Simon's parents and Mr. Gilbert) were prepared for Simon's legendary WardrobeMalfunction. It's right, none of them knew that when Joe Thomas entered the stage, his left testicle would stick out from his clothing. So any laughing or shock from the audience's side is probably genuine.
* HeyItsThatGuy: Neil's AmbiguouslyGay dad looks a lot like AmbiguouslyGay [=MP=] [[Series/TheThickOfIt Julius Nicholson]].
** Tara was a character in the short lived, oft-forgotten yet fairly popular [[Creator/TheBBC CBBC]] show Kerching. Due to the age of the target audience a lot of people who grew up watching Kerching had a HUGE Hey It's That Girl moment when she turned up.
** Wait, was that [[Series/TheSarahJaneAdventures Rani Chandra]] at that party?
** Will's Dad is [[Series/BuffyTheVampireSlayer Giles]] - and he's a DICK!
** Do not say that Series/BabylonFive [[BerserkButton is a big pile]] [[Series/{{Spaced}} of shit]] to Simon's dad.
** Is that you, [[Film/TheColorofMagic Bethan]]?
** [[Film/HarryPotterAndTheHalfBloodPrince Cormac McLaggen]] is Ben in the [[Film/TheInbetweeners2 second film]].
* LifeImitatesArt: Simon (Joe Thomas) and Tara (Hannah Tointon)'s on screen relationship may have ended disastrously, but they are now together off screen.
* NamesTheSame: A differently spelled first name it may be, but Carli shares quite a lot of similarity with Carly from Series/{{iCarly}}, especially considering they both have a DoggedNiceGuy who has a JustFriends crush on them (Simon for Carli, and Freddie for Carly). In the fashion show episode, Carli uses the line "Please for me" on Simon to get him to do something for her, which is identical to a line that Carly constantly used on Freddie to get him to do things she wants. Although the similarity of the two ends the further towards the end of the series and TheMovie TheInbetweeners gets.
* RealLifeRelative: Anthony Head, who plays Will's Dad, is the real-life father of Emily Head, who plays Carli.
* RecycledScript: The motorbike scene at the start of Series 3 Episode 3 was originally written for the [[Film/TheInbetweenersMovie film]] but cut and repurposed for TV series.
** In the [[Film/TheInbetweeners2 second film]], dialogue in some scenes that were cut is reused in other scenes:
*** Neil's InfoDump about his irritable bowel syndrome originally took place in a scene on the group's flight to Australia.
*** In a voiceover during the Splash Planet sequence, Will mentions that Jay insisted that the water in the park was "80% vaginal fluid". Jay originally said this about the Lazy River ride in the same scene.
* UnintentionalPeriodPiece: Definitely can be seen as one to the late noughties: the soundtrack is taken from that period, mobile phones used by the characters are of the pre-smart phone variety and there are no tablets, characters use [=PS3s=] and Nintendo Wiis, social networks in use are Facebook, [=Myspace=] and Bebo (The latter two of which have fallen out of favour since), while Twitter, Snapchat and Instagram are not (though Neil uses Grindr in the second movie).
* WhatCouldHaveBeen: The original opening scene of the [[Film/TheInbetweeners2 second film]] featured [[Film/TheForceAwakens Daisy Ridley]] as one of the party hosts. When the scene was reshot, Ridley was unavailable to reprise her role.
* WorkingTitle: The pilot episode was entitled ''Baggy Trousers''. Joe Thomas named the cast's 'band' on the radio after the final show's working title of ''1, 2, 3, 4''. This was most likely a reference to the song by Feist of the same name, which was something of a Leitmotif during the first series and appears sporadically throughout the rest of the show.
** ''Sex On The Beach'' for the first movie, which became its MarketBasedTitle in Germany.
** The second movie got a few although they were much more clear cut; ''The Inbetweeners Down Under'', ''The Inbetweeners Movie 2'' and ''The Inbetweeners 2: The Long Goodbye''. The latter was what appeared on all the scripts and (strangely) is the title that appears on Blu-Ray copies when read by the player.