Calendar Factory Firing

Listen up, numbskull! This joke is funny because the dude took "a day off" from a calendar factory. "A day off" is also like a single calendar page. Get it? I bet you didn't, you cotton-headed ninny muggins. The joke uses wordplay, which is one of the earliest known forms of humor. Wordplay is a literary technique and type of wit in which words are used in a skillful and amusing way.