Knock-knock Who's there? Fuck. Fuck who? You.
Knock, knock; Who is there? Love; Love who? U, U, U!
Knock knock Who's there? Double. Double who? W!
Knock,Knock, Who is there? Pen! Pen who? is...
Knock-knock Who is there? A shattered penis with many diseases. What kind of illness? Gall, Aids, Gonorrhea, Syphilis... Enough, it is the best present for my mother in law.
Knock Knock! Who's there? Testicules. Testicules who? Pillow for penis .
Knock-Knock Who is there? A long penis with a naked head. Come in please we were waiting for you.
Knock, Knock Who is there? A long erected penis with an eye on my head and some wools in my feet. What do you want? Is there any body to suck me? I want to weep.
Knock, knock! Who's there? Spell. Spell who? W-H-O.
Fast way to screw up someone's Knock Knock joke...? "It's open."