Will's dad. Who is revealed to have left Will and his mother to marry a woman barely older than Will. He insults Will, his hobbies and casually admits he didn't invite him to the private wedding, containing a mere 'couple of hundred' close family and friends.
Neil, surprisingly. He spends a large portion of the film getting with all manner of girls on the boy's holiday. Towards the end he reveals that his girlfriend dumped him and he didn't want to dampen the mood. Turns out he was lying, his girlfriend Nicole is waiting for him at the airport during the credits.
Kavorka Man: Neil. He's extremely thick and yet he seems to get offers left, right and centre! Though, to be fair, he's not exactly picky. The other guys have to literally drag him away from the next dinner lady who comes onto him.
Lack of Empathy: Combined with some arguably correct logic by Will when he discovers the parents of a wheelchair-bound girl have reserved loungers by a pool. ("Hang on. You're not disabled, and she doesn't need anywhere to sit!")
Jay says this when his mother and sister catch him masturbating. It's a little hard for him to explain because he has diving gear on his head.
Done later by Richard, when he mentions he phoned his parents to come and pick him up. Before this it's implied that Richard is some kind of dodgy character who's spent all his money on drugs.
A more traditional variant also occurs when Nikos is found cheating on Alison.
Race for Your Love: Parodied when Simon decides to swim to shore from the boat party to declare his love for Lucy. Everyone cheers as he jumps into the water only to stop cheering as he struggles to make it to shore, has to be rescued by emergency workers, is taken to the hospital, and shits himself. Also a case of Reality Ensues.
Throw the Dog a Bone: Could be said to be the entire point, after all the stuff the gang went through in the series.
Running Gag: Jay orders that every time Simon mentions the name Carli, he must be slapped in the balls. He says her name a lot.
Sex as Rite-of-Passage: All the boys except for Neil. Even though Simon and Carli were dating, it's implied that they did not have sex together, so everyone but Neil is a virgin and presumably they all lose their virginity on this trip as well as gaining 'independence'.
The Silent Bob: Lisa doesn't speak until the scene where she verbally attacks Richard's mother, mistaking her to be making a move on Neil.
Also an example of Hand Wave - Simon just says "not moving to Wales" in the opening minutes to brush it off
Suspiciously Similar Substitute: Considering that Lucy isn't at all like Carli, Jane is not like Chloe, and Lisa doesn't seem to be like Neil's flings, it's noteworthy how Alison is essentially just Charlotte with the Alpha Bitch traits (both the good and the bad) turned down. They are even somewhat similar in appearance. Though it may be justified in that Will already found his perfect type of woman in Charlotte, and then he naturally falls for Alison who is so similar, while the others lads' matches had formerly been... less than perfect.
Wimp Fight: When two of the guys get into a fight, the other two actually just stand there and discuss whether to help. During the entire conversation, neither of the combatants manages to injure each other, and there's multiple shots of people laughing in the background.
Would Hurt a Child: Jay pushes a kid who can't swim into a pool for de-pantsing him in front of the entire poolside.
Wrong Genre Savvy: Lucy seems to know of the Romantic False Lead trope, but to her misfortune, she tries to resolve it like one would resolve it in a more sappy romantic movie. During the movie, Simon grows to like her more and more, but he still keeps his ridiculous, one-sided crush on Carli. When Simon sits on the beach moping because he cannot go to the boat party with Carli, Lucy tells him how sorry she is for him and offers him her (expensive) ticket so that he can go. In a romantic movie, this act of compassion and unselfishness would probably make Simon forget about Carli, realize that how much better of a girlfriend Lucy is, and get together with her, possibly ending with a Big Damn Kiss - and this is obviously what Lucy hopes for. Instead, Simon grabs the Jerkass Ball and just anti-climactically snatches the ticket from her, after which he runs to the boat to find Carli. He gets better later though.
Your Cheating Heart: Alison's Greek boyfriend Nikos. Will even accurately predicts what he says to excuse his cheating.