Line a 9x13 pan with parchment paper, set aside.
In a large pot add butter and melt over medium heat.
Add marshmallows and cook until smooth and melted.
Remove from heat.
Sprinkle in dry cake mix, stirring well after each addition. You want to make sure there are no cake mix lumps.
Add rice krispies and sprinkles and stir until combined.
Press rice krispie treats into your prepared pan.
For thicker treats use an 8x8 and for thinner treats use a 9x13.
Sprinkle the top of the treats with more sprinkles.