St. Peter is very busy in Heaven, so he leaves a sign by the Pearly Gates: "For Service Ring Bell."
Away he goes; he barely gets started when BING! the bell rings. He rushes back to the gates, but no one's there.
St. Peter goes back to work when suddenly BING! the bell rings again. He rushes back to the gates, but no one's there. A little annoyed, St. Peter goes back to work.
Suddenly, BING! the bell rings again. St. Peter goes back; again, no one's there, and he's now really, /really/ irritated.
"Okay, that's it," he says. "I'm going to hide and watch to see what's going on." So St. Peter hides, and a moment later, a little old man walks up and rings the bell.
St. Peter jumps out and yells, "Aha! Are you the guy who keeps ringing the bell?"
"Yes, that's me," the little old man says.
"Well, why do you keep ringing the bell and going away?" St. Peter asks.