Preheat your oven to 350F. Move the rack to the middle position, and grease an 8x8 baking dish.
Add the yellow cake mix, eggs, and melted butter to a large mixing bowl. Using an electric hand mixer, mix well until combined.
Stir in the sprinkles and white chocolate chips.
Transfer the batter to the 8x8 pan (it will be a thick batter). Spread it out as evenly as you can.
Bake for 23-30 minutes or until a toothpick comes out pretty clean. Keep in mind that the batter will set a lot when it cools. I baked mine for 30 minutes; 25 minutes does leave these blondies a bit under-baked for my taste.
Cool the cake batter blondies in the pan (place it on top of a cooling rack) for at least 20-30 minutes (preferably until they're fully cooled).
Cut the blondies and store them in an airtight container for up to a few days.