I was making a world, and just for fun, I tried to put in a Lemniscale (∞). I got what I call the "Dirt screen", and the game crashed. That's really all that happened.
The summary of the crash report was as following:
---- Minecraft Crash Report ----
// Hey, that tickles! Hehehe!
Time: 10/20/13 8:32 AM
Description: Updating screen events