I gather that there are a few musicians on the forum, and as you probably know, musician jokes abound. A typical one is:

Q. What do you call a pretty girl on a trombone player's arm?

A. A tattoo.

Anyway, the following is my favorite, and can be re-purposed to make fun of just about anyone you like. Best for artistic types, though:

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A little boy is walking down a city street with his mother when they pass a music store. He runs over to the window, fascinated by all the guitars, drums, horns, etc. in the window. As his mother walks over to him, he says, "Mommy! Mommy! I want to be a musician when I grow up!
To which his mother replies, "Now, Sweetheart, you can't do both."