Preheat oven to 325 degrees F (160 degrees C). Spray a 10-cup bundt pan with non-stick baking spray, or grease pan generously and sprinkle with flour, turning and tapping the pan so that the flour evenly coats all the nooks and crannies of the pan; set aside.
Make the Cake Batter: In a large bowl, whisk together the Yellow Cake Mix (1 box) and Instant Vanilla Pudding (2 box) until well combined. Add the Vegetable Oil (1/2 cup) and Water (1 1/4 cup) and blend with a hand mixer until well mixed.
Add the Egg (4), one at a time, beating just until combined after each egg is added. Don’t overmix! This batter is thicker than a traditional cake batter.
Make Cinnamon Swirl: Place 2 cups of the prepared cake batter and add the Ground Cinnamon (2 tablespoon), Brown Sugar (1/3 cup) and Milk (2 tablespoon); stir until well combined.
Pour half of the Cake Batter into the bottom of the prepared bundt pan. Using a ½-cup measuring cup, pour half of the Cinnamon Swirl batter on top of the Cake Batter. Next, drizzle the remaining Cake Batter evenly on top. Finally, spoon the remaining Cinnamon Swirl Batter on top.
Using a table knife, gently pull the knife blade through the batter, swirling the batters together gently – only a time or two around the pan.
Bake in preheated oven for 45 minutes, then turn pan ½ turn and lightly tent with foil. Continue baking for an additional 45 minutes.
Remove from oven, remove foil and cool cake in the pan on a wire rack for 15 minutes.
Invert cake onto your serving platter and cool completely.
Insert the King Cake Plastic Baby: It is tradition to tuck a small plastic baby into the bottom of the cake, or a whole Almonds (to taste), which signifies good luck to whoever gets that piece of King Cake! NOTE: DO NOT BAKE THE KING CAKE WITH THE PLASTIC BABY! Insert it into the bottom of the cake after it is cooled, by tipping the side of the cake up slightly and pushing the plastic baby into the bottom. You can also use a whole almond in place of a plastic baby.
Prepare Cream Cheese Frosting: Combine the Cream Cheese (2 ounce) and Unsalted Butter (2 tablespoon) and beat until light and fluffy (with either a hand mixer or an electric mixer). Add Powdered Confectioners Sugar (2 cup), Pure Vanilla Extract (2 teaspoon) and ¼ cup of the Half and Half (1/3 cup). Blend slowly, adding additional half & half until the frosting reaches the consistency you want for drizzling.
Divide the Cream Cheese Frosting into three separate small bowls, add a few drops of Food Coloring (to taste) and stir well so that you have one bowl of yellow, one bowl of bright purple or violet, and bright green.
Drizzle each color of Cream Cheese Frosting on top of the cooled cake. Sprinkle with holiday Sprinkles (to taste) (if desired).
Serve immediately or store airtight at room temperature for up to 3 days - if it lasts that long! Like most bundt cakes, the cake becomes moister and more flavorful the longer it sits.