Christmas is an annual festival across time and space: it's been known to occur on Mobius, the Special Zone, and at least one alien planet. It may also take place on Earth.
The origins of Christmas have never been explained. On all planets, however, it's followed by a period of gentle snowfall. Traditionally, it is a time of being with friends and family, having good cheer, and doing good deeds. Notable customs are carol singing, Christmas feasts, and the giving of presents.
Linked to Christmas is the powerful entity Father Christmas, sometimes named Santa Claus, who delivers presents to children across the entire universe.