I don't know how much of a pun this is, but here's another true one.
Mister and I were at a reenactment, and I got a small rip in my dress when it got hung on a very long bolt sticking out of the porta-pot door. Same thing happened to my friend Janine about two hours later. Later that night, we were singing around the tent and making quite merry, when the Fair Becky came back from the ball. "I'll be back to join you in a minute, after I go to the blue box."
"Be careful," we said.
"Why?" she said.
I said, very loudly, "Janine and I tore our dresses from the screw in the portajohn."
As soon as I said that, boyoboy was I ever sorry. ;-)