Terence Tao explains quantum theory as a game of Tomb Raider:
Imagine first that Lara is about to navigate a tricky rolling boulder puzzle, when she hears a distant rumbling sound - the sound of her player saving her game to disk. From the perspective of the player, what happens next is the following: Lara navigates the boulder puzzle but fails, being killed in the process; then the player restores the game from the save point and then Lara successfully makes it through the boulder puzzle.
Now, how does the situation look from Lara's point of view? At the save point, Lara's reality diverges into a superposition of two non-interacting paths, one in which she dies in the boulder puzzle, and one in which she lives. (Yes, just like that cat.) Her future becomes indeterministic. If she had consulted with an infinitely prescient oracle before reaching the save point as to whether she would survive the boulder puzzle, the only truthful answer this oracle could give is "50% yes, and 50% no".
It gets weirder from there, but it's a fun read. And since everybody else in the physics blog world has linked to it before me, I'll throw in a gratuitous image.