If it ends up on your wall, you're probably retarded.
They break their nose!
When you throw your knickers against the wall, and they stay there.
You can mash potatoes, but you can't pee soup. (sorry sorry. Really. I've loved this joke since I was... oh.. six...)
A mashed potato.
They never stop to ask directions.
I can make it to the end of a Jimmy Kimmel joke without laughing.
Anyone can mash potatoes!