Based on material from the popular "Just Joking" department of National Geographic Kids, these three books are packed with 900 knock-knocks, tongue twisters, riddles, and more. Photographs appear throughout, and a poster is included as well. Readers 9 to 12 can't resist this stuff: What do you call a super-cool rodent? An awesome possum. What uses a gallon of paint and 100 brushes? A centipede getting a pedicure.