Joke: Math teacher: You can't use y to represent a single point!
Student: Y-naught?

Joke: What is the best way to keep water from running?

Joke: Knock knock!
Who's there?
Who's Duff?
Who's duff who?
You da foo!

Joke: What do you get when you mix your dad's red paint with his white paint?

Joke: Why shouldn't you write with a broken pencil?

Joke: Why do golfers wear two pairs of pants?