The entire scene where Wells is having his stomach wound dressed by Cooper and Megan. The whole time, Wells is completely and utterly drunk, having been drinking to help cope with the pain of having his intestines hanging out.
Wells:(regarding Cooper) I tell you what, I love him. (to Cooper) I love you! Like the mate that I... that I love.
Earlier during the same scene, Wells glances down at his exposed intestines:
It's made even funnier thanks to the DVD Commentary: According to Sean Pertwee, he really did down three quarters of a bottle of brandy, and Kevin McKidd wasn't in a very good mood. Pertwee said something that upset McKidd, and thus the latter's punches - right in Pertwee's face - were entirely real, and he was too pissed to realise it until the next day.
Terry inadvertently saving Sam the dog's life (Ryan was about to shoot him to make him stop barking)... by vomiting all over Ryan's head.
A short while later, Terry utters this gem after Cooper asks him if he's okay:
Terry: I've got a real craving for a kebab.
During the siege, Spoon is frantically trying to nail a door shut. Cue a werewolf shoving its hand through the letterbox. Spoon's reaction? Hammer the bastard's fingers!
Earlier, Joe is shooting at one of the werewolves through a window with a shotgun. The werewolf's response? Grab the gun from him, shoot at him with it (he jumps out of the way in time), and then toss it back in after him.
Near the end, Wells is hiding in a closet, and holding off a werewolf with an improvisedAerosol Flamethrower, and yells at it, "Go away!" The choice of words, and the tone he says them in, just seem rather hilariously out of place given the context.