MacReady lives at the end of "The Thing".
He travels through the Antarctic wilderness for days, surviving on what little nourishment he can find.
Just when all hope is lost, and he has resigned himself to a lonely icy death, MacReady discovers a tribe of Elves living in almost complete isolation, deep in the unexplored, snow-covered Antarctic plains.
The Elves have long told tales of the prophecy of the arrival of a bearded man, who will show them their true calling. They proclaim MacReady's arrival as the realisation of this prophecy, and worship him as a god.
In an attempt to rid himself of the horrific memories of what happened at U.S. Antarctica Research Station 31, MacReady gratefully accepts the new name that the Elves have given him; "Santa Claus".
Santa Claus, having narrowly prevented the spread of an Alien infection around the world, decides to spread love, joy, and gifts around the world instead. Together, Santa Claus and the Elves travel the world and deliver presents to children across the globe. In honour of this, the tradition is repeated every year on the night of December 24th.
A Legend is born.
"The Thing 2: The Christmas Chronicles"