There's a young couple in the cinema. The girl says, "I must have a piss, can I squeeze past you?"
"Why don't you squat down on the floor and do it" says the boyfriend. "You'll have to disturb all these people, besides its dark, no one will see you."
"OK" she says. She pulls her drawers down and squats on the floor. The bloke starts feeling horny at the thought of her down there, so he reaches down and makes a grab.
He feels something long and hard and says, "Urgh! Have you changed your sex?"
"No" she says "I've changed my mind... I'm having a shit instead."