Math Concepts With Funny Names

(Some of this came from a Reddit post  I read, and some of  the comments on it.) 

Here are theorems with names that I think are funny or unusual. The names are also pointers to the Wikipedia entry on them or some other source.

The Chicken McNugget Theorem

The Ham Sandwich Theorem

The Hairy Ball Theorem

Freshman Dream

The law of the unconscious statistician

The Homicidal Chauffeur Problem

The Pigeonhole Principle (We are so used to this we no longer find it funny, but it is.) 

Eventown and Oddtown 

I am sure there are more and I invite you to comment BUT there are some issues

1) What is funny?

2) I want math concepts that are known. As a counterexample, if Lance proved a theorem and called it the Funkytown Theorem just to get on this list then I'd be surprised. It also would not count. 

3) The name has to be some relevance to the concept. 

And I now list two titles of papers that I find funny. Note that what I write IS the title, even though the first one is an odd title and the second one really does not look like a title.

A minus sign that used to annoy me but now I know why it is there (two constructions of the Jones polynomial)

Some title containing the words "homotopy" and "symplectic", e.g., this one