Lily: Marshall, I love you, but there's lots of reasons to have sex.
Marshall: Name one.
Lily: I can name 50.
Marshall: No, you can't.
Lily: Number one: Last Thursday.
[flashback to Lily in bed with a sleeping Marshall at 3:45 a.m.:]
Lily: Hey, Marshall, want to do it?
Marshall: I'm up.
[present:]
Marshall: You befouled our marital bed because you couldn't get to sleep?!
Lily: You're the one who said, "That shadow on the ceiling looks like a scary toothless clown. Good night, Lily."