Actor Allusion: 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.
Dawson Casting: 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 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.
Enforced Method Acting: 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 Wardrobe Malfunction. 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.
Tara was a character in the short lived, oft-forgotten yet fairly popular 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.
Life Imitates Art: Simon (Joe Thomas) and Tara (Hannah Tointon)'s on screen relationship may have ended disastrously, but they are now together off screen.
Name's the Same: A differently spelled first name it may be, but Carli shares quite a lot of similarity with Carly from iCarly, especially considering they both have a Dogged Nice Guy who has a Just Friends 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 The MovieThe Inbetweeners gets.
Real-Life Relative: Anthony Head, who plays Will's Dad, is the real-life father of Emily Head, who plays Carli.
Unintentional Period Piece: 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 favor since), while Twitter, Snapchat and Instagram are not.