William Shakespeare is the supposed inventor of the Knock Knock joke. Most scholars suggest that the first ever Knock Knock joke was told in Shakespeare’s second play titled Macbeth. Specifically, there’s two Knock Knock jokes told in act 2, scene 3 of this well-known play. 

“Knock, knock! Who’s there, i’ the name of

Beelzebub? Here’s a farmer, that hanged

himself on the expectation of plenty: come in

time; have napkins enow about you; here

you’ll sweat for’t.

Knock, knock! Who’s there, in the other devil’s

name? Faith, here’s an equivocator, that could

swear in both the scales against either scale;

who committed treason enough for God’s sake,

yet could not equivocate to heaven: O, come

in, equivocator.”