Someone who pointlessly knocks on the door.
Apple the door myself!
Matt.
Someone knocking at your door for no apparent reason.
Burglars don't knock!
A pure bred meth lab.
Gingerbread. Edit: This is more of an out-loud joke. So, maybe it'll help if it read: "Ginger-bred" instead.
Dind Dong
Nobody asks, 'who's there ' when you try and tell a knock knock joke.
Well I'll be damned!
Lay awake, contemplating the existence of Dog.