Dr. Knucklehead is knock-knocking at the door and children will happily answer, because they love knock-knocks--and these are the very best. Try this: "Knock Knock." Who's there? "Daisies." Daisies who? "Days he's a man, but by night, he's a werewolf!" Or laugh a lot at this: "Knock Knock." Who's there? "Billows." Billows who? "Bill owes me ten bucks and he said you'd give it to me." Every one is riotously funny.