Not the only one I've heard, I've heard millions. But its the only one I can always remember, the one that reliably bubbles up into my consciousness when someone says, "Tell a joke.".

I first remember Cheech Marin telling it, although I doubt he invented it. It's probably been around in one form or another since Christ was a corporal. For some obscure reason, it seems to strike a profound and existential chord in me. It goes something like this...

Straight Man: "Why don't Baptists make love standing up?"

Punch Line: "Because they're afraid someone might see them and think they're dancing."