Punch-line in Punchline, you set up a joke, than someone else posts the punchline and a new joke setup.
Example:
Dude1: knock knock, who's there, boo, boo who? Dude2: Why are you crying? why did the chicken cross the road? etc. Rules: 1 No inappropriate jokes or punch lines. 2 No spam. 3 No Jokes that make absolutely no sense 4 Forum rules still apply.