The Joke

"Stop me if you've heard this one before. A man walks into a bar--"

"Stop."

"I haven't even finished yet."

"But you said to stop you if I've heard it."

"You don't know what the joke is."

"Sure I do. A man walks into a bar..."

"That's just the beginning."

"The beginning of a joke I've heard before."

"Look, here's the punchline. The extra long one's for the dog."

"Oh, I guess I haven't heard it before."

"Well, now it's ruined."

"No, start over."

"Okay, a guy goes into a bar--"

"No, that one I've heard. Tell the new one."