If that Santa Claus single has stickers on it for the portrait and signatures, it's worth $1 with the stickers removed. If the bill is printed that way, it's an interesting question whether the secret service would consider it to be a counterfeit, or not. My guess is they would, so it would be worth a few years board and lodging at a federal graybar hotel. If they decided that it's enough different from a real bill to be legal, IMHO it's worth a few cents.
I also have one of the "Santa" dollars. From the documentation I have it is legal tender. I will have to break it out and post. Here is a link with some information. http://santaclausdollar.com/