After partying at the casino the other night I was walking my dog along the country road next to the parking lot (she waits in the car) when I saw a woman that I know standing next to her car. Jokingly I yelled out, "Hold it right there. You're under arrest."
She looked stunned for a moment and then broke out laughing when she saw it was me. Unbeknownst to me, her girlfriend had just squatted by the bushes next to the road and was taking a pee when I yelled out.
So she thought she was in big trouble, and the only relief she got was in not getting arrested. She still had to pee, and badly.
What's funny is that the joke came off without my even seeing her there.