Bender: A naked blonde walks into a bar with a poodle under one arm and a two-foot salami under the other. She lays the poodle on the table. The bartender says, "I suppose you won't be needing a drink." The naked lady says, <falls through ceiling>"OHH SHIIIT!"
Made even funnier because that was improvised, apparently, and because we never hear the end of it.
The scene where Bender takes a screw out of the door so it won't stay open, and the hilarity that ensues.
And when Vernon gets Andrew to help him to prop the door open:
Bender's genuine bewilderment at Claire's lunch. Even Claire finds it funny, and in a good-natured way.
"Can I eat?" "I don't know. Give it a try."
The lunch scene in general is pretty hilarious, but some of the best was Andrew pulling endless amounts of food out of his bag, only to find the rest of his classmates looking at him in shock before exclaiming 'What's your problem?'
Everyone's "what the hell" expressions at Alison's lunch.