Can he swing, from a thread? No he can't, he's a pig...
He's not Spiderpig any more, he's Harry Plopper!
Speaking of the movie, this troper thinks everything Grandpa does with his prophecy, and everything afterwords related to his prophecy is gut-bustingly funny.
Grandpa (referring to himself): "That crazy old man in church was right!"
Also, Homer's attempt to save his family that literally puts him between a rock and a hard place.
"Run! Run! Run! Jump! Jump! Land! Land! Rest! Rest!" and "Why does everything I whip leave me?"
Ralph Wiggum: (watching a naked Bart skateboard by) "I like men now!"
Cargill's line after going mad with power. "You ever try going mad without power? It's boring, no one listens to you."
And right before that line, when he angrily throws his binoculars at the dome only for it to bounce back and whack him in the face.
Homer's road signs. "Look, we can't keep stopping at every 'sop', 'yeld', or 'one vay' sign we see."
Homer trying to scare people with a fake chainsaw making chainsaw noises, and one of the unheard lines in Simpsons history:
Marge Simpson: Somebody throw the goddamn bomb!
The Comic Book Guy's guess as to what EPA stands for: "I believe it was the sound the Green Lantern made when Sinestro threw him into a vat of acid. Eeeeeeee....pah!"
The brief but memorable usage of the cutaway gags that cropped up in the film had this troper laughing so hard his sides were literally starting to burst. Namely, this one:
Russ Cargill: Don't you worry. We've devised a solution that will take Springfield off the map... forever.
(Cut to a man driving in a car with a built-in G.P.S. system, containing a massive nuclear tower representing Springfield)
Female G.P.S. Voice: Coming up on your right...
(The nuclear tower representing Springfield blinks out of existence)
I don't know if this is the right place for it, but here's the [1] entry that tropers can migrate here if they want.