You MUST do the following to make a lego Santa!
At the Mos Eisley Cantina, enter the following two codes: CL4U5H (for Santa hat and red clothes) and TYH319 (for white beard Extra).
Then, go to the Character Maker and create your Santa costume! Use a human head, the red clothing, and the red cap! Then give him either a red or green lightsaber. The color of the lightsaber will depend if he's naughty or nice! Then go to the Extras menu, and activate Disguise 3. And go to Free Play in any level to test your Santa!