Write a dumb joke, but it's Peter Griffin from Family Guy overexplaining it to Lois.
Peter: "Knock knock"

Lois: *no response*

Peter: "You're supposed to say, 'Who's there'? so I can tell you this hilarious joke I found on the internet."

Lois: "All right, who's there?"

Peter: "Ha, good one, uh, Alpaca."

Lois: "Alpaca who?"

Peter: "Alpaca tuna sandwich for my business trip tomorrow, ha. Get it, Lois? It's a play on words, the 'alpaca' sounds like 'I'll pack' and then a tuna and then the trip. Oh, never mind Lois."