Prepare three 8" pans with non-stick cooking spray and set aside.
Put Rice Krispy Cereal in a large bowl and set aside.
In a large pot, melt butter and mini marshmallows on medium heat. Make sure you stir every 15-30 seconds until everything is melted.
Mix in vanilla.
Add marshmallow mixture to Krispy cereal and mix until everything is coated.
Let Krispy mixture sit for 1 - 2 minutes to cool.
Add about 1/2 cups sprinkles and lightly mix.
Divide the mix evenly between the three cake pans. Spray your hands with non-stick cooking spray and press down until the layers are tightly packed and have an even top.
Place in the refrigerator for at least 30 minutes.
Once cooled, use an offset spatula to remove the layers from the pans and decorate.