Annoying Guy: *obviously drunk* Knock Knock!

Me: *sighs* Who's there?

Annoying Guy: *chuckles under breath* Cow goes.

Me: *rolls eyes* Cow goes who?

Annoying Guy: NO! Cows go moo! OWLS go who! *laughs annoyingly*

Me: *dunks rest of drink on his head* Yep, bye.

*slaps head* How could I never think of that joke?