Mischievous players of either faction can earn the "Scrooge" achievement by tossing a snowball at either King Magni Bronzebeard in Ironforge or Cairne Bloodhoof in Thunder Bluff during the festival.
To Earn the "Fa-la-la-la-Ogri'la" achievement, players must complete the level 70 "Bomb them Again" quest while mounted on a flying reindeer.
To earn the "Crashin' and Thrashin'" achievement, use your [Crashin' Thrashin' Racer] to crash into 25 other players' cars during the festival.
The "Let it Snow" achievement is the reward for those who manage to use a [Handful of Snowflakes] on each of the following race/class combinations: Orc Death Knight, Human Warrior, Tauren Shaman, Night Elf Druid, Undead Rogue, Troll Hunter, Gnome Mage, Dwarf Paladin, Blood Elf Warlock, and Draenei Priest.
There are two separate faction version of the "Bros. Before Ho Ho Ho's" achievement. Alliance players must use [Mistletoe] on all of the following "Brothers" throughout Azeroth: Brother Nimetz in Stranglethorn Vale, Brother Wilhelm in Goldshire, Brother Kristoff in Stormwind, Brother Karman in Theramore, Brother Joshua in Stormwind, Brother Crowley in Stormwind, Brother Cassius in Stormwind, Brother Benjamin in Stormwind and Brother Anton in Nigel's Point.
The Horde version is a bit easier, as players of that faction only need to seek out Brother Malach in the Undercity, Durkot Wolfbrother in Warsong Hold, and Brother Keltan in Icecrown.
To earn the "A Frosty Shake" achievement, use a [Winter Veil Disguise Kit] to become a snowman and then dance with another snowman in Dalaran.