Talk to the Ghost of the Cow King Put the Staff of Herding in your inventory (it's not necessary to equip it). Note that the staff is permanent and it is not consumed; in fact, you can replay the Whimsyshire level as many times as you like.
On console, only 5,000 gold is needed and Leoric's Shinbone and the Liquid Rainbow are not required for crafting the staff. The plans for this staff drop randomly from Izual in any difficulty mode.
The Staff of Herding allows players to access the zone Whimsyshire, not to be confused with Whimsydale, which is accessed through a Rainbow Goblin's portal. This page details how to obtain the materials for the staff, craft it, as well as the possible rewards of Whimsyshire.
The Nightmarish Staff of Herding was a craftable staff in Diablo III. It was needed to access Whimsyshire on Nightmare difficulty. As of version 2.0, any version of the Staff of Herding will grant the player access to Whimsyshire on any difficulty, so it is no longer necessary nor possible to upgrade the staff.
When she spawns, she has a rare chance to drop the Gibbering Gemstone. The item will be account bound as soon as it drops. There is also a bounty quest to kill Chiltara, which may make finding the Huntress easier. Gemstone drop rate is approximately 5%, but as of patch 2.0.
The Black Mushroom is an item used to craft the Staff of Herding, which can be used to gain access to Whimsyshire. It can be found on Level 1 in the Cathedral (Normal difficulty).
Put the Staff of Herding in your inventory (it's not necessary to equip it). Note that the staff is permanent and it is not consumed; in fact, you can replay the Whimsyshire level as many times as you like.
Wirt's Bell is a miscellaneous crafting material in Diablo III, it is used to construct the Staff of Herding which is necessary to access Whimsyshire. It has an Item Level of 1 and requires a character level of 1.
I think the drop rate is somewhere between 2% and 5% (without MF). Here is an important Note: The "Plan: Staff of Herding" is a legendary item and thus it is affected by Magic Find. If you have a very high MF > 300 % you will get the Plan very often.
Some herding breeds relied on barking in order to help them move animals.
The dogs can follow the shepherd's command to herd in sheep from over a half mile away. Because they spend so much time together, shepherds and dogs form a close social bond. Part of the herding dogs skill is innate (under genetic control or instinctive) and part is learned behavior (what you teach the dog to do).
What difficulty level are you farming it on? Keep in mind that a while back, Blizz made all mats, including Gibbering Gemstone, a higher droprate on higher torment levels. So if you are speed running normal, or even low torments for it, you should just instead do T16 runs for it.
The drop rates are roughly a 5% chance from a Pinata (Hamburger) and a 10% chance for a Spectrum from any unique (read: purple named) mob. It can be a long time before you find one, but certainly can be rewarding.
Whimsyshire is a Secret Level, or secret land, in Diablo 3. When you enter the Secret Level of Whimsyshire a Feat of Strength along with a Banner and Sigil are unlocked. You can run the Whimsyshire level as many times as you want and you will get the In The Land Of Killer Unicorns achievement for finding it.
The Liquid Rainbow is a miscellaneous crafting material in Diablo III, it is used to construct the Staff of Herding which is necessary to access Whimsyshire. It has an Item Level of 1 and requires a character level of 1. "The colors swirl and twist in hypnotic patterns."
You can retrieve Wirts Leg as many times as you like, and use it as many times as you like, in any difficulty without any reprecussions except ONE. If you kill the Cow King in the cow level, on any difficulty, you will be unable to open the portal yourself to go to the cow level in that difficulty again.
Some breeds, especially those in the Herding Group, possess an instinctual drive to move animals around. Herding behavior can become a problem if your dog begins herding your kids or nipping your ankles. Training, brain games, and dog sports are all effective ways to channel herding instincts into other outlets.
Whimsydale is a unique location in Diablo III that can only be accessed by killing a Rainbow Goblin. It uses the Whimsyshire tileset, and is overall identical to it. This location was added in patch 2.1.
Leoric's Shinbone is a miscellaneous crafting material in Diablo III, it is used to construct the Staff of Herding which is necessary to access Whimsyshire. It can sometimes be found in the fireplace of Leoric's Manor in Act I.
The Infernal Staff of Herding was a craftable staff in Diablo III. It was needed to access Whimsyshire on Inferno difficulty. As of version 2.0, any version of the Staff of Herding will grant the player access to Whimsyshire on any difficulty, so it is no longer necessary nor possible to upgrade the staff.
While Whimsyshire most exists for the portrait frame and the sense of accomplishment, getting to go to Whimsydale means lots of gold, crafting materials and gemstones. It rivals the Realm of Greed in terms of pure financial reward and loot to be on offer.