Quote from Chandler in The One Where Chandler Can't Remember Which Sister
Joey: Ask Chandler. He fooled around with her. She told me you said you could really fall for her. Is that true, or are you just getting over Janice by groping my sister? Chandler: It's gotta be the first one. Joey: Really? That's great. You and my sister, sitting in a tree. Chandler: Yep, I'm in a tree.