SON: "Knock knock." DAD: "You're trespassing." SON: "What?" DAD: "You're not allowed on my property. I have signs." SON: "No, you're supposed to say 'Who's there?'" DAD: "You've triggered the home defense system. You are being recorded. Please try not to move. The bear repellant turrets are very sensitive." SON: "Knock knock. Who’s there? Dad. Dad who? Dad, the most annoying knock-knock joke ruiner ever." DAD: "Trespasser identified. Access authorized. All systems standing down."