The Next Wave was the first game in the franchise to feature a special version of the game (an edition) based around certain holidays. Chicken Invaders: The Next Wave – Christmas Edition was released on 25 November 2003, and was initially intended to be available during the months leading up to Christmas, however, its popularity caused InterAction studios to release this, and all subsequent Editions as standalone games. The Christmas Edition of The Next Wave replaces game graphics, sounds and music with festive versions and elements related to the Christmas holiday.
[Source: wikipedia.org]