The Tooth Is Out There - S3.E23

Ned has lost a tooth, and left it under his pillow for the Tooth Fairy. When the fairy comes, though, Newton thinks he's a burglar and attacks him. This results in the Tooth Fairy cursing Ned to have giant teeth, and Ned can only have the curse lifted if he does several tasks for the Fairy, such as counting all the newts in the world and doing his laundry.