Crimboween was the result of a KoL Halloween falling on the real-life date of Crimbo/Christmas on December 25, 2006. It was uniquely distinct from previous Crimbos for its combined Nightmare Before Christmas and A Christmas Carol inspired theme along with a new quest, Save Uncle Crimbo!, which spanned the month of December.
Combinations of real-life and in-game holidays are rare: the next time this particular combination could possibly happen directly is (insert date here) - although there is a possibility that in 2048, where KOL's Halloween appears on Boxing Day (December 26), may be close enough to provide an excuse for a joint holiday.
October 31st 2006 (Real life Halloween) was the first (and possibly only) Halloween during which Trick or Treating could yield cups of eggnog, fruitcakes (without wearing Crimbo Duds), gingerbread bugbears, or candy canes (without wearing Bow Tux). A Crimboween memo was also passed out stating that Uncle Crimbo and his helpers were running Halloween that year instead of the Scream Queen.
A Lonely Crimbo Elf appeared in The Big Mountains. When spoken to, he assigned the Save Uncle Crimbo! quest.
A Spooky Advent Calendar appeared in the Campground of every player. As each day was punched out, a special Crimboween item was given, varying depending on the day. If a player had not yet used a chocolate lump, one would also be given. A new section became available every day.
Players could also sleep as much as they wanted at their campsite, even if they didn't need to, in order to complete the quest.
All players received a tropical Crimbo pressie in their inventory, granting tropical wrapping paper and a special item when opened. Players who had helped rescue Uncle Crimbo received an additional bonus item.
All alternate versions of Crimbo Town disappeared from the Big Mountains.