Some were taught to me by @alien. Please add your own!
  1. How do you tell the sex of a chromosome?
    Pull its jeans down.
  2. Why can't Cinderella play soccer?
    She's always running away from the ball.
  3. How do you make a tissue dance?
    Put a little boogy in it.
  4. What's brown and sticky?
    A stick.
  5. What's red and smells like blue paint?
    Red paint.
  6. Where does the President keep his armies?
    In his sleevies.