There are several new additions for 2013 including the Rotten Little Helper – a new battle pet from the Stolen Present daily reward. I managed to get mine off the third try (see below).

Rotten Little Helper

Rotten Little Helper (Humanoid)
Abilities: Club, Booby-Trapped Presents, Greench’s Gift, Ice Lance, Ice Tomb, Call Blizzard.

Note that while the Rotten Helper Box is rare, the pet itself is uncommon and can be caged so expect to see these in the AH. It’s also been reported that a couple of SoO bosses are dropping the santa hats.

The special gift will be the Crashin’ Thrashin’ Flyer Controller found under your faction’s capital city tree as well as two achievements – Crashin’ Thrashin’ Flyer and The Danger Zone.

Players will also be able to purchase the 2012 Winter Veil gifts: Foot Ball and The Pigskin from Toy Vendors Blax Bottlerocket, Clockwork Assistant, Craggle Wobbletop, and Jepetto Joybuzz if exalted with the vendor’s faction.

~~~

You’re a Mean One… (daily) requires you to save Metzen the Reindeer and recover some stolen treats after defeating The Abominable Greench. Completing the quest rewards you with a Stolen Present and a small chance to contain a Lump of Coal which can summon Lumpy as well as a Miniature Winter Veil Tree.

Just make your way to the Growless Cave in the Alterac Mountains (south of the Ruins of Alterac) to find the Greench standing guard outside his cave.

There’s no need to race and tag but you may require a group of 2 or 3 to kill him.

Taken from Wowhead

He randomly casts Abominable Crush on players or other objects (winter veil trees) that appear throughout the fight – You’re supposed to run out of it like with Blitz from the first boss of Grim Batol (otherwise huge damage and getting knocked in the air = +fall damage). Snow Crash freezes a player for 6 seconds and deals a bit of damage. This can NOT be cancelled with PvP trinket! It’s cast by the Snowman spawned from Throw Strange Snowman. It is reported that you can avoid Snow Crash if you move far enough away from the Snowman. The Abominable Greench doesn’t hit that hard himself, but the freeze makes it really hard to kill solo unless you have quite good gear and are a blood DK you have to find a small group, maybe a healer but if everyone runs out of  Abominable Crush there isn’t that much damage coming. Throw Winter Veil Tree is also cast during the encounter. The Winter Veil Tree is a valid target for Abominable Crush.

Once he’s defeated, multiple gift bags will spawn which any player can loot. As long as you loot a bag and speak to Metzen within 5 minutes of the Greench’s death, you will complete both criteria for an easy hand-in.

A-Caroling We Will Go requires you to use your Gaudy Winter Veil Sweater (also available to purchase from the General Goods vendor) to carol in your enemy capital cities during the Feast of Winter Veil.

In 2012, we had the transition of Winter Veil pets into Battle Pets:

with the addition of several animations:

The best part is they no longer cost a Snowball to summon.

For more info, check out WoWHead’s complete Feast of Winter Veil 2013 Guide.