Line a 8x8 or 9x9 inch baking pan with parchment paper, or coat with cooking spray. Use can use 9x13 pan for thinner rice krispies treats.
In a large Dutch oven or saucepan, melt butter over medium low heat.
Set aside 1 cup of the mini marshmallows and add the remaining marshmallows into the saucepan and stir until completely melted.
Remove from heat, then stir in vanilla extract.
Add 1 cup of marshmallows, rice krispies cereal, candy coated chocolate, and sprinkles, then gently stir to combine. It's okay if some of the chocolate candy melts, it'll add to the flavor.
Transfer to the prepared baking pan. Use a silicon spatula to gently press down until evenly distributed. DO NOT press down too hard or they'll be overpacked and hard once cooled.
Add a few extra candy coated chocolate and sprinkles on top, press down gently, then let the rice krispies treats set for 1 hour.
Remove from pan, cut into squares, and enjoy!