Knock knock. Who's there? (Knock knock.)

(Knock knock) who? Oh, for goodness sake, you just started the joke again! This is an endless loop!

Knock knock. Who's there? Mango.

Mango who? Mango-nificent to meet you!

Knock knock. Who's there? Alpaca.

Alpaca who? Alpaca the suitcase, we're going on vacation!

Knock knock. Who's there? Wendell.

Wendell who? Wendell you give in to the sheer pun-ishment of this joke and finally admit it's been weighing on you, a real heavy hitter in the groan department, making you wonder when 'til the end of this tale of wordplay woe?