A complete guide on Whimsyshire, including how to obtain each and every part required. [Enhanced Version: http://youtu.be/bOXDNUkm2C8] Table of Contents below:
Changing Quests 0:04
Black Mushroom 0:15
Leoric's Shinbone 0:45
Wirt's Cowbell 1:29
Liquid Rainbow 2:00
Gibbering Gemstone 2:53
Plan for Staff of Herding 4:07
Crafting the Staff of Herding 5:48
Finding Whimsyshire 6:29
Fighting Whimsyshire 7:36
NOTE1 (proven to be FALSE):
Enter through Leoric's Entrance. If you see a large spiral staircase as you enter, then the Black Mushroom has spawned.
[FALSE - the spiral staircase has zero relation to if the Black Mushroom has spawned or not]
The Mysterious Caves can also spawn in the alcove South-West of the Oasis Waypoint.
In order to get to Whimsyshire in Nightmare, Hell, or Inferno, you must go to the Quartermaster in Act IV after you beat the game in the difficulty. That Quartermaster will then sell you the new Plan. Teach the Blacksmith the new Plan then use the previous Staff of Herding to upgrade it for your current difficulty (new Staff will still work for older difficulties).
Cost to craft:
Normal - 50,000 gold
Nightmare - 200,000 gold
Hell - 500,000 gold
Inferno - 1,000,000 gold
AS OF PATCH 1.0.3 - PLAN PRICE CHANGE
Once I verify some of my previous notes and gain some footage (work schedule allowing), I will re-upload a revised version that contains additional information and extra tips!
Music (in order of appearance):
Tristram (Diablo II)
For the New Lunar Republic http://youtu.be/sf0tYs5U5RI
No Strings Attached (Octavia Battle Theme) http://youtu.be/sLmAlskhRZc
Escape from the moon (nightmare moon) http://youtu.be/9PoXCo1roGs
Twilight's Sonata [Twilight's Theme] http://youtu.be/Or482ar7fi4