What do you call a group of cows singing Christmas carols?

A moo-sical choir

Why did the Christmas carolers bring a ladder to the party?

They wanted to hit the high notes

Why did Santa consult a meteorologist every December?

He needed accurate "snow-casts" for his delivery routes.

Why did Santa's reindeer start a union at the North Pole?

Because they wanted to deer-legate their workload and get more rein-deer-ence pay!