Ever heard of "Where's Waldo?"? Well... this is the real life Christmas version of that game.
You'll need to prepare before your party. Get a bunch of Rudolf figurines, pictures and other Rudolf stuff. Use your imagination... you can also play a movie where Rudolf appears during your party.
Can you find all the Rudolfs?
When you think you have enough Rudolfs, place them around your house. Try to hide them and make them blend in as much as possible.
When your guests arrive, inform them that you'll be playing the "Where's Rudolf?" game. Anyone that finds a Rudolf gets a point. At the end of your party, the person that has the most points is the winner.
It's also a good idea to get a Christmas themed prize for the winner of the game. It's the best way for people to really get into it.
You can make the whole thing more popular by placing a big score board in the middle of the party area, so that everyone can see how others are doing.
Have fun playing and have a merry Xmas!