(Monica, your childhood best friend, with whom you've done everything together But just recently, the person you always thought was a boy surprised you. You were teasing 'him' about your recent gains at the gym when, out of nowhere, she suddenly takes off her trench coat that she has been wearing for half of her life and reveals that she is indeed a girl. She burst into laughter)

 "BWAHAHA! You thought I was a boy?!"