I explained Santa to the little girl tonight.

Santa is a Timelord. He travels all around the world in a single night because he can travel in time. Because he can travel in time, it doesn't matter how much he needs to do. His sled is a TARDIS, able to materialize inside any house in the world. Because he only needs to eat a few cookies a day, he doesn't swell into gigantic proportions as he eats all those extra calories that people provide to him.

Santa has a sled that has a sack that can hold all the toys, because it is bigger on the inside than it is on the outside. He gets extra trips in per voyage by shoving all the cookies into his bag and taking them back to his elves who only need sugar to live on. That, and The Ladn of Sweets always needs new construction materials to avoid Peak Candy.

Santa knows who has been naughty and who has been nice because he can go into the future and ask you about all the bad things that you did as a child. Not knowing any better, and finding Santa a rather chatty fellow, you will tell him.

Santa, like all Timelords, goes by his title rather than a name. There are many saints, but if you say Santa, you mean one specific saint.

Also like other Timelords, Santa is known for his specific outfits. The outfits change as Santa regenerates.