Knock, knock. Who's there? Lettuce! Lettuce who? Lettuce in, it's cold out here! From the first knock-knock joke to the last, Lettuce In! provides the perfect introduction for young joke tellers. With whimsical animal characters and easy-to-follow jokes, this book also features a flap on every spread. The flaps reveal the surprise punch-line to each hilarious knock-knock joke!