Automatic Association:

Let me introduce you to The Game. By the way, you all just lost the game. Oh, and so did I. Haha, well most of you probably know what it is, but for those who don't, it works like this:

    1) You are always playing the game. You can never stop playing.

    2) When you are not thinking about the game, you have won.

    3) The moment you start thinking about it again, you have lost.

While The Game is an interesting look into game theory, let's skip over that.  It becomes interesting when I throw in a fourth rule:

    4) When you hear the phrase "pink hippopotamus" you will think of the game.

This rule seems a bit confusing.  The first three are easy enough to enforce.  They're just conditions. However, the fourth rule is odd. 
How can I possibly enforce it? 
The truth is I don't need to.
Memories form in chains and the neurons connect, therefore, if you remember one thing, it leads to you remembering another. If you want to remember one thing, you have to remember the chain leading up to it.  

Basically, what rule 4 did was connect your memory of the game to your memory of the phrase "pink hippopotamus." It's not permanent, as the connections between your neurons are always changing. Sometimes you'll remember it, sometimes you won't but the association will always be there.

Now go say "pink hippopotamus" to someone. While they will be completely and utterly confused, you will be loosing the game. Then you will explain why you said "pink hippopotamus" and they will also loose the game.

(Credit for the idea as well as most of the writing goes to: http://foamingmind.blogspot.com/)

Have a fantastically dandy day, everybody!