You seem to be new to the game.
Whimsydale has been around for a while now and the actual level with the staff(Whimsyshire) has been in the game since release of D3.
It is also referred to as Pony land mostly and it is not the cow level, there is an actual cow level(whole rift) with 10 levels and a boss and sometimes an event aswell.
http://youtu.be/SymLU-xxyng
Whimsydale has been around for a while now and the actual level with the staff(Whimsyshire) has been in the game since release of D3.
It is also referred to as Pony land mostly and it is not the cow level, there is an actual cow level(whole rift) with 10 levels and a boss and sometimes an event aswell.