Knock, knock . Who's there? Radio . Radio who? Radio not, here comes a lot of funny jokes! The bestselling jokesters The Hennessy Kids are back again to make you laugh - now with their first book of knock knock jokes! Knock on all your family & friends' doors and share this great collection of jokes with them so you can all enjoy laughing & groaning together for a fun time. The Hennessy Kids are authors of the bestselling joke books 101 Halloween Jokes , 101 Christmas Jokes , and 101 Pet Jokes .