Q: Why did the cookie go to the doctor?
A: Because it was feeling crummy

and of course...

our favorite knock knock joke where the "who" is "interrupting cow". The joke is to yell "Moo!!" before the other person can finish saying "Interrupting cow who?"

The best part is that the joke can be recycled with interrupting chicken...interrupting duck....interrupting goat...

A barn yard worth of laughs!