Q: Why do reindeer have red noses?
A: They are not equipped with ABS and thus tend to bump into things on
slippery surfaces. This is why Santa is often seen with a red nose (the sleigh doesn't have an airbag, either). 

Q: Why does Santa use Elves?
A: There is no trade union for Elves. They're easy to exploit. 

Q: Is there really a Mrs. Claus?
A: Highly unlikely. Since Santa is surrounded by male figures (Elves, reindeer named Rudolph, Donner, Blitzen etc.) his sexual preference seems to tend towards homosexuality. He is said to have some problems finding a gerontophile/zoophile Elf for a threesome with a reindeer, though. 

Q: Does Santa really live on the North Pole?
A: Uncertain. However, rumor has it that the story of Santa and the North Pole has nothing to do with the Arctic, but that Santa is known to frequently ask the Elves and reindeer if he can shove his pole up north.
Obviously, this is related to the cryptic description "up where the sun don't shine", which applies to both the North Pole and assholes in general. 

Q: Does Santa really work all year round making toys?
A: Get real! Check the box in which the Christmas gift came! Does it say "Made on the North Pole"? ("Made in China", more likely) 

Q: Then what does he DO all year?
A: Uncertain. Chasing Elves and reindeer, most likely. Maybe he spends his winters in Florida. 

Q: Is the story about the little angel and the Christmas tree true?
A: Without a doubt. Santa has a temper and can develop a nasty attitude (he doesn't take stress too well). 

Q: If so, why do the little angels on Christmas trees look happy (given the fact they have a tree up theirs)?
A: Little angels are known to be kinky. 

Q: Do the polar bears on the North Pole cause Santa any trouble?
A: Not since Santa equipped the guard Elves with M-61 submachine guns. 

Q: So Santa is basically a gun-crazy, homosexual, angry old man who exploits little Elves, fools around all day, and drives around in a sleigh that lacks basic security measures?
A: You forgot about the bestiality thing.