A new poster in Pokémon Center's in Japan has indicated that a Happinas will be distributed from November 19th, 2011 to December 25th, 2011. Visitors to the Pokémon Center's can say "Merry Christmas" to a Pokémon Center Staff Member and receive a calendar card with a serial number on it to unlock Happinas via the Japanese Pokémon Global Link's Dream World. Happinas has the hidden Ability Healer. Further details regarding the event will be released after October 29th, 2011.

Source: http://d.hatena.ne.jp/asami-1120/20111015