Jesus, I could go on FOREVER about the films, so I'll just do AHDN for now... :p
When George literally faceplants the floor, and John looks back and laughs his head off.
Ringo: "Well since he's your grandfather, who knows? HAHAHAHAHAHAHAHAHAH!"
"Hey Mister, can we have our ball back?" Especially when they're suddenly running alongside the train, Paul knocking on the window!
John: "I bet you can't guess what I was in for!"
Paul's Grandad: "Chicken sandwiches and cones of caviar... disgusting."
George: "Put your tongue away! It looks disgusting, hanging out all pink and naked!"
And pretty much the entire bathroom scene.
Ringo's delayed laughing fit when asked how he likes his girlfriends to dress.
"I bet his wife doesn't know about her." "He's probably not got a wife, look at his sweater!" "She might have knitted it!" "She's knitted him!"
George: "Sorry we hurt your field, mister!"
Pretty much the entire George scene with the shirts, especially "I wouldn't be seen dead in them. They're dead grotty!", "Once we wrote these letters saying how gear she was, and all that rubbish" and "We turn the sound down on her and say rude things... have I said something amiss?"
John: "I now declare this bridge open!"
John: "MY NAME'S BETTY!"
...and I'll shut up now before I quote the whole film! :