What is Your Best Friend's Sister?
1.
a stupid comeback phrase that's used for virtually everything, even if it doesn't make any sense whatsoever
Friend #1: dude! i saw your mom last night! she was hot!
Friend #2: your best friend's sister!
Friend #!: you have a sister!?
dude: what happened last night!?
dude 2: your best friend's sister!
dude: shut up!
See
