We in the English speaking world use Santa Claus, Father Christmas and Kris Kringle as three interchangeable names for the same non-existent person, responsible for teaching children not to trust their parents. Then we have Saint Nicolas, which is also often used synonymously with these, but sometimes also refers to an alleged historical figure who lacked the reindeer and sled, the penchant for cookies and milk, omniscience about whether we've been bad or good, the elf workshop at the North Pole, and pretty much all of the fun stuff.
What I find interesting about this is the question of how we could possibly determine that at least the first three of these names refer to the same person if that person doesn't exist. To compound this problem, consider the fact that in the Christmas traditions of Germany and some other places, the etymological equivalents of these names do not all refer to the same non-existent person, but to different non-existent people! There's Nikolaus (corresponding etymologically to either Saint Nicolas or its derivative Santa Claus) who delivers presents via a donkey on the night of the 5th/6th of December, often leaving chocolates or other small items in your shoes (not the most hygienic place to store chocolate in my opinion). He dresses in a very ostentatious red and has a white beard suspiciously like what English speakers associate with Santa Claus, but Nikolaus prefers a more saintly looking hat and carries a shepherd's staff.
