My son told me this one. I hadn't heard it before.
Son: Why did the chicken cross the road?
Me: I don't know.
Son: He was going to visit the dummy.
Son: Knock, knock
Me: Who's there?
Son: The Chicken
In spite of my misgivings about the search capabilities that are available it would appear that I should have at least checked the top of /r/Jokes. Ahem. The chicken had the right address...