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

java.lang.ArrayIndexOutOfBoundsException: 8734
at azz.a(SourceFile:473)
at azz.a(SourceFile:507)
at azz.a(SourceFile:494)
at bai.i(SourceFile:476)
at bai.e(SourceFile:180)
at bai.d(SourceFile:170)
at bai.b(SourceFile:99)
at bai.a(SourceFile:284)
at bbb.a(SourceFile:284)
at bbw.l(SourceFile:258)
at bbw.k(SourceFile:217)
at ayw.o(SourceFile:1302)
at ayw.ad(SourceFile:755)
at ayw.e(SourceFile:706)
at net.minecraft.client.main.Main.main(SourceFile:103)