There are a lot of these "what people think I do" versus "what I do" gags going around. Some are pretty funny. Here's one on policing. The intellectual in me thinks of the Rashomon Effect. The kid in me just giggles at seeing Lou Costello in a police uniform.
[thanks to Stef the Greek]
[Hey all you folks, consider buying my book, Cop in the Hood. It's good.]