What's the stupidest joke you know?

Here's mine:

A panda walks into a bar and orders his food and drinks. When he's done, the panda gets up and pulls out a gun, which he then shoots into the ceiling. He promptly leaves.
The next day, the panda goes into the same bar, at which point the bartender says, "Hey! You can't come in here after what you did yesterday, you didn't even pay!"
To which the panda says, "bartender, look up the definition of a panda in the dictionary."
The bartender opens his dictionary to "panda" and reads aloud, "panda - eats shoots and leaves."