Diablo - so the developers took that urban legend and made it real in Diablo II, complete with attacking, mooing cows.
This time, one might recall all the complaints from some Diablo fans when the initial screenshots of the game came out, accusing the developers of making the game too bright and colorful - forgetting of course that Diablo II had its own bright levels, such as Lut Golein.
Well, there's a new secret level in Diablo III, and takes the original complaints to the Nth degree, with a new My Little Pony-ish level called Whimsyshire, full of smiling clouds, rainbows, and multicolored unicorns.
You can see the insanity on display in the video below. A nice little "Take that!" from the developers to those whining fans.