Sally jumped out a plane, she forgot her parachute!
Knock knock.
Who's there?
Not Sally...
How did she die?
A bomb came down whilst falling through the sky.
Knock knock.
Who's there?
A bomb.
Knock knock. Who's there? Hal. Hal who? Hal will you know if you don't open the door?
What happened when two invisible giants knocked over their blocks?
9/11.
9/11 was a round of Clash of Clans. They knocked down two towers, not three.
Why did the chicken cross the road? To visit the idiot.
Knock knock.
Who's there?
The chicken.
The chicken who?
*Silence*
Knock, knock.
Who's there?
Stranger.
Stranger who?
Stranger, why are you in my house masticating my apparent dead wife?
Knock knock. Hwoo's there? Far from home. Hwoo's far from home? Spider-Man.