The end of the very first episode. After grassing and making all of his classmates hate him at the pub (including Jay and Neil), Simon decides to stick with him.
The final episode of series one when the boys all jump together on the trampolines.
The episode Girlfriend has Simon warning Will that Charlotte will break his heart. Will disagrees and the two argue bitterly and go their separate ways. After Will messes things up with Charlotte, he sees her looking for a new man at a charity dating game, the final twist of the knife. Later, when he's at home with his mum, Simon and Jay come over to invite him to come and watch Neil on his own embarrassing date. The fact that these two (particularly Jay) would go out of their way to cheer Will up is really quite nice, especially considering how cynical the show usually is.
The group hug from the film.
Followed by Jay giving up his bed to Will when he goes to sleep in the anthill.
"Do you want a lager, Si?"
Neil's offer to buy Jay chips after being dumped.
Just before that, a drunken Will comforting Jay.
The entire sixth form standing up for Will and telling Donovan to leave him alone in "Xmas Party".
Simon reluctantly letting Will come with him when he goes to Tara's sister's house, because Will admitted he gets lonely without the other three around.
Donovan threatening Will if he hurts Charlotte, in a way.
Although it was also fairly hilarious, especially considering what happened shortly afterwards, but Neil asking Simon whether or not he and Jay should look after Will after Simon has moved to Swansea was fairly heartwarming. He just worries about Will, that's all.
Jay setting Simon up with Becky at the Caravan Club meeting. Sure, he embellished a few details about her and Simon makes a complete balls of it, but it shows that Jay does have some redeeming qualities and genuinely wants Simon to forget about Carli and find someone better for him.
Will putting an arm around Jay and comforting him when he starts crying after his girlfriend dumps him.
The part in the second film where all the boys hold hands as they think they're going to die in the Outback. The fact that Will and Jay are the first to hold each other's hands is pretty heartwarming as well. Doubles as a bit of a Tear Jerker, particularly the part where Neil and Jay hold hands, even if it is slightly Played for Laughs.
Will's apology to Jay as well, for leaving him instead of helping him find Jane.
Will realising that he would rather spend time with his true friends rather than a girl who doesn't really care much for him. It's telling that he's willing to risk being sick on a small plane just to catch up with them.