Stephen Hawking's Favorite Song

Listen here, Levi, you are not too bright. This joke uses wordplay. You see, the song "Head, Shoulders, Knees, and Toes" is a common children's song about body parts. But instead of "knees and toes," the joke says "screws and bolts" because Stephen Hawking uses a wheelchair, which has screws and bolts. It's funny because it makes a connection between his physical condition and the song. Get it?