Knock knock. Who's there? Mom & Dad. Mom & Dad who? Exactly. -Cool way to tell your son he's adopted.

Knock knock. Who's there? John. John who? John proceeds to break into tears as his mother's alzheimers has progressed to the point where she doesn't even remember him.

Knock Knock Joke (created by a 4yo) Knock knock - Who's there? Apple - Apple who? *pause* APPLE NOTHING! APPLES DON'T SAY ANYTHING! YOU'RE SO WEIRD, DADDY!

My friends mom just died And I asked him if I could tell him a joke to cheer him up. He said sure but I don't think it will help. Here is how it went. Me: Knock Knock Him: Really dude a knock knock joke? Ok, who's there? Me: Not your mom.