Much like your mom and that's
what she said, this phrase has a high potential to add
innuendo to a previously-uttered statement. Can also be used to
augment a comeback.
Person 1: Dude, you suck.
Person 2:
No, YOU suck. At night.
Girl 1: So, how are things between you and your boyfriend?
Girl 2: Great! I've never met anyone so awesome!
Asshole 1: At night, that is.
Person 1: I like
chillin' with my
homeboys. At night.