Blizzard introduced a new world event achievement named Day of the Dead, which runs through November 1-2. It isn't part of the world event meta-achievement, so don't worry ... you can still get your Violet Proto-drake without completing this achievement.
To get started go to the graveyard of Orgrimmar, Undercity, or Thunderbluff (Horde). Alliance can go to the Stormwind, Ironforge or Darnassus graveyard. There you will find two NPCs:
Catrina and
Chapman. Talk to Catrina, and type /dance. That's the achievement. Not too hard. If you have Wrath of the Lich King installed you can go to the Dalaran graveyard, next to the Violet Citadel and the Underbelly sewer entrance. Catrina and Chapman are there too.

Grab the
Bread of the Dead recipe from Chapman and learn it. Requires Cooking. If you don't have cooking profession, go to your cooking trainer. You don't need to level up cooking to be able to cook Bread of the Dead. It only requires a Simple Flour and a Ice Cold Milk.
Go to Orgrimmar/Undercity or Ironforge/Stormwind and buy the
Ice Cold Milk from the
Innkeeper. The
Simple Flour is sold by Trade Vendors and Cooking Supplies Vendor.
Important: Don't cook the Bread of the Dead in other cities. It's not certain if it is a bug, but if you hearthstone to Dalaran or travel via Boat or Zeppelin from Eastern Kingdoms or Kalimdor to Northrend, the
Bread of Dead will disappear from your inventory. Just keep the ingredients with you. Go to Dalaran's graveyard by the Violet Citadel and stand by the Ghostly Cooking Fire located next to Catrina.
Click on the Bouquet of Orange Marigolds (hold in off-hand) or eat an Orange Marigold. Both are sold by Chapman (Day of the Dead Vendor). This will allow you to see the ghosts and spirits dancing on the graveyard. There you will see Cheerful Dalaran Spirit.

He will give you the quest titled:
The Grateful Dead which asks you to cook a Bread of Dead and to give it to him. You need to cook it right there in Dalaran and turn in the quest. He will reward you with a
Macabre Marionette. It is a tiny skeleton holding the classic
maracas (percusion instrument) and wearing the typical Mexican hat. More details of Day of the Dead available at the official website
here.
Pop Culture Reference
In real life, the Mexicans celebrate the
Day of the Dead, a tradition which is celebrated from November 1-2. Mexican families gather to celebrate and to honor their dead family members, or friends. They cook Bread and candy in shape of skulls, and other ornamental food. Prepare a altar or table full of all kind of food crafted to be placed by the tomb of their deceased ancestors. The tradition has been cross-referenced with ancient Mayan and other Mexican native indian festivities which they used to dedicate to the goddess Mictecacihuatl -- known as the "Lady of the Dead" -- also known as
The Catrina.