From Bulbapedia, the community-driven Pokémon encyclopedia.
Christmas (Japanese: クリスマス Christmas) is a winter holiday celebrated throughout the Pokémon world. Much like the secular aspects of the Western holiday in the real world, people wait for Santa Claus to come down their chimneys and deliver gifts and goodwill to them.
In the games
In Generation II, many Pokémon were given away at the New York Pokémon Center as part of the Gotta Catch 'Em All campaign. Each week, a different set of Pokémon were distributed. From December 21 to 27, 2001, the week was Christmas week, and a Delibird with Pay Day (as an Egg) and a Celebi were distributed.
In Generation III, many Pokémon were given away at the New York Pokémon Center. On Christmas Day 2003, a Kingdra, Zangoose, Seviper, and Milotic were distributed as part of this campaign.
In 2011, to celebrate Christmas, fans could greeting staff members in a certain area of Japanese Pokémon Center stores, and if they did they would receive a small calendar card called the "Happy Calendar" with a unique password included on the back. This password could be input into the Pokémon Global Link to receive a Blissey. This Blissey could then be sent to a Generation V game using Game Sync. The password could be redeemed from November 19 to December 25, 2011.
In 2012, the Pokémon Center Tohoku Victini was distributed to all Generation V games at Pokémon Center stores to Celebrate Christmas. This Victini was available form November 25, 2012 to January 3, 2013.
In 2013, a Scyther holding a Metal Coat and a Haunter without a held item were distributed via trade to players with a copy of of either of the Pokémon X and Y games to Pokémon Center stores and select Toys "R" Us stores across Japan. These Pokémon both had the original Trainer "Christmas" (in Japanese). Since they were both distributed via trade, they would undergo evolution as soon as the player received them. Furthermore, a serial code to obtain a Lucky Egg was also given out at Pokémon Center stores to any players who brought a copy of Pokémon Black or White, Pokémon Black 2 or White 2, or Pokémon X or Y; the serial code could only be redeemed in Pokémon X and Y.
In the anime
In the dub of Island of the Giant Pokémon, James's Koffing was revealed to be a Christmas gift. In the Japanese version, it was a year-end gift.
Episodes featuring Christmas
In the manga
Manga chapters featuring Christmas
Magical Pokémon Journey
Pokémon Chamo-Chamo ☆ Pretty ♪
Pokémon Gotta Catch 'Em All
Pokémon Pocket Monsters
Pocket Monsters DP
Pocket Monsters BW
In the books
Books featuring Christmas
In the TCG
The Flaaffy from the Expedition Base Set features Flaaffy sitting underneath a Christmas tree next to a collection of presents.
In other media
Pokémon Christmas Bash is a CD album with a collection of Christmas-themed Pokémon songs.