This outrageous book features hundreds of hilarious knock-knock jokes for kids, along with hundreds of clever illustrations. Knock-knock. Who's there? Lettuce. Lettuce who? Lettuce in and we'll tell you another knock-knock joke! Knock-Knock. Who's there? Venice Venice who? Venice dinner? Knock-Knock. Who's there? Police. Police who? Police open the door! Knock-Knock. Who's there? Luke. Luke who? Luke before you leap.