In Calvin's Easter basket he had a package of these toddler tub crayons. They are the best $4 the Easter bunny ever spent. They are round and just the right size for little fists to grasp. Even when it's not bath time, he wants to sit in the tub and draw. The crayons at this point are worn down little stubs, but he's drawn over every surface of the tub enough that he's still convinced he's creating colors every time he catches an artistic fancy.
