Greg Davies, who played the role of Mr. Gilbert; worked as a teacher of Drama and English for thirteen years in real life. He later gave up his teaching career to become a stand-up comedian.
Matt Smith, who later became the eleventh Dr. Who auditioned for the role of Will, but lost out to Simon Bird. Iain Morris recalled - "He was brilliant - down to the last two for Will, I think. I think he was a bit too dashing! That's why he'll be brilliant in Doctor Who (2005) - he's got something sort of heroic about him. He had the humour, but what I think Simon Bird has got is a sort of vulnerability and so when he's doing these terrible rants at people, you know he's the loser! Whereas there's something very leading man and heroic about Matt Smith."
There are only two scenes over the entire series which do not feature at least one of the Inbetweeners; in Xmas Party (2008), Mr. Gilbert is talking to himself after the school prom. And in Work Experience (2009), Will's Mum and Neil's Dad have a meeting with Mr. Gilbert about their sons' work experience.
The four main characters are in their mid-to-late teens, but when the first episode was broadcast in May 2008, the actors playing them varied in age from 20 (James Buckley) to 24 years of age (Joe Thomas).
A one off special entitled The Inbetweeners: Fwends Reunited (2019) aired on New Year's Day 2019. It received overwhelming disdain from critics and fans of the series, much of which stemmed from the fact it was a talk show rather than a reunion episode; James Buckley later made a public apology.