GUIDE ON HOW TO GET THERE.
The zone is called "Whimsyshire"

Step 1 (Get all these items)
- A "Black Mushroom" which spawns in cathedral level 1 from Act 1
- A "Shinbone" which is located randomly in the fireplace in leorics manor Act 1.
- "Liquid Rainbow" is located from a mysterious cave in a mysterious chest in the oasis in Act 2. To get into the mysterious cave you have to find a monger who doesn't spawn in every game but the spawn point is always the same!
- A "Wirt's Bell" which is sold from the little girl (a monger) in the city on Act 2. (100.000 gold)
- "Gibbering Gemstone" drops from Chiltara a random mob in the caverns of frost Act 3(A little hint: This is the area where you destroy the ballistae.)
- "The plans" drops randomly from Izual on Act 4.

Step 2 (Build the staff)
If you got all these items you have to build the staff. (50.000 gold)
Build it at the blacksmith.

Step 3 (Simply walk to the Whimsyshire level)
You have to walk from new tristram to the street to old-tristram. You will find a red glowing slit with a dead cow infront of it. The rest is self-explanatory.

Goodluck, and have fun.

FAQ:
The plans are only dropped from the boss, yes.
The staff is permanent.
There is one version for all levels with diffrent price tags!

You have to find the recipe for the staff, as a drop.

This post was edited by LurkinFishie on May 17 2012 12:11pm

screen shot that uve been there.

Don't need to, the zone is already confirmed.

Link please.
I wanted to see how it looks like...

Word, there's an article on Forbe's website. Vote to sticky this!

https://www.youtube.com/watch?v=LB0XHZ7Ee1o
A few minutes in you can see it.

http://www.fz.se/artiklar/nyheter/20120517/diablo-3-motsvarigheten-till-secret-cow-level-funnen

Swedish gaming site but yet another proof =)

which quest is it to kill izual i forget?

Don't remember the exact quest name, sorry. He's on the bridge part though if I remember.

LMAO