Someone who pointlessly knocks on the door.
Because they are a-door-able.
So they can open doors of opportunity for their students.
She had no arms. Knock knock Who's there? Obviously not Sally
Yoda lady. Yoda lady who Good job yodeling! 2.Knock knock. Whos there Well, not your parents, because your parents never knock!
Ginger-bred
A pure bred meth lab.
Nobody asks, 'who's there ' when you try and tell a knock knock joke.
The mafia doesn't like witnesses.
He didn't believe in higher powers!
Someone who shows up to your door for no reason.