Blend cake mix, egg, butter, and eggnog/milk in a bowl with a blender until evenly mixed. Stir in some sprinkles.
Spray an 11 x 7 baking pan with nonstick, and spread on half of the batter in one even layer. Sprinkle on a layer of white chocolate chips, then spread on the rest of the batter.
Add some more sprinkles on top.
Bake at 350 degrees for 25 minutes or until bars are a golden color.
Once out of the oven, let them cool for a few minutes and cut into squares.