I'm a newbie about enjoying the english joke.
I read about the "Knock Knock" joke about the interrupting cow.
But I don't quite know what does "the interrupting cow" mean.
Is there some background about it?
I think that a cow was chosen for this joke because "moooo" (what an English cow says) rhymes with "who." Also, people are sometimes called cows when they are rude and obnoxious. Any animal could have been chosen but a perhaps for these two reasons a cow was chosen.