I remember in Space Balls probably two of my favorite scenes.
1. "I... am your father.... 's brother's former room mate's dry cleaner" Or what ever it was.
2. When the Chestburster pops out of "Kane's" chest and he says "Oh not again" as the Chestburster starts to sing and dance.
"It's the one that says Bad Mother ****er." - Jules Winnfield... Describing his wallet, Pulp Fiction.