In his first year at Hogwarts, Harry Potter discovers the Mirror of Erised, and Dumbledore explains that the mirror shows each individual their "heart's desire." (Unless you're a real dummy, you already knew that since Erised is Desire backwards. I mean, everyone else held each page up to a mirror as they read, right?)  Although the mirror is used for dramatic effect in the book, the internet has used it to make hilarious memes. Enjoy!