Preheat the oven to 350 degrees F. Grease a jelly roll pan with non-stick cooking spray. Set aside.
Prepare the cake mix according to the package directions. Pour into the prepared pan and bake according to the listed directions (usually 12-18 minutes).
Remove from the oven and cool to room temperature in the pan on a wire rack, about 1 hour. Cut the cake into small cubes. (I did a 10 x 11 grid.) Set aside.
In a large mixing bowl, beat together the pudding mix, milk, and vanilla extract with a hand mixer on medium-low speed until smooth and thickened, about 2 minutes.
Add the cream cheese and powdered sugar and beat until smooth. Fold in Half of the Cool Whip with a rubber spatula until evenly combined.
Assembly
Arrange half of the cake squares in a layer at the bottom of your trifle bowl so it's covered. Spread half of the pudding mixture over the cake. Repeat these layers once more so the bowl is filled.
Top the trifle with dollops of the remaining Cool Whip and add Christmas sprinkles for garnish. Chill in the fridge until you're ready to serve.
Notes
If you don't have a Jelly Roll pan available (10 x 15 x 1 baking sheet), you can prepare the cake according to the package directions for a 9x13 pan. The cake will need to cool for about 2 hours since it will come out thicker.
I would also recommend cutting the cake cubes in half (vertically) to create smaller cubes, so you have enough for each layer.
If you prefer, you can use 3 cups of prepared whipped cream instead of Cool Whip.