Darn, you weren't supposed to catch that. Have you ever heard that joke?

Little Johnny had to use the bathroom, so he asked his teacher to be excused, but she said no. A couple minutes later, he asked again. She said that he could go, as long as he recited the alphabet first. So he said:
"A, b, c, d, e, f, g, h, i, j, k, l, m, n, o, q, r, s, t, u, v, w, x, y, z."
To which the teacher replied, "Good, but where's the 'p'?"
"It's running down my leg!"

Okay, I didn't say it was a good joke...