Because you touch yourself at night...

Peter Griffin: Jeez! This hangover's killing me.
Peter Griffin: I haven't felt this crappy since I went to that museum.
[Flashback]
Peter Griffin (as a child): Why did all the dinosaurs die out?
Museum Docent: Because you touch yourself at night.

For some reason I always get reminded of Family Guy, but unfortunately I've a bad memory and may forget some of their quotes. Well, hopefully these sites will put an end to that: Family Guy Quotes and Planet Family Guy