Make Cups: Grease two 12-cup muffin tins and the bottom of a shot glass with cooking spray.

Melt Butter and Marshmallows: In a large saucepan over medium heat, melt the butter and marshmallows, stirring occasionally, until smooth.

Stir in Cereal: Remove from heat and quickly stir in the Fruity Pebbles cereal until evenly coated.

Form Cups: Divide the warm mixture between 16 muffin tin cups. Press down on the mixture with the greased shot glass to create wells, forming the “cups.”

Chill: Transfer to the refrigerator and chill before removing from the muffin tin, for at least 15 minutes. This allows the cups to set and firm up.

Make Cheesecake Mixture: Meanwhile, make the cheesecake filling. In a large bowl using a hand mixer, beat the softened cream cheese, sugar, melted white chocolate, and heavy cream until smooth.

Fold in Cool Whip: Using a rubber spatula, gently fold in the Cool Whip until combined.

Fill Cups: Spoon the cheesecake mixture into the chilled Fruity Pebbles cups.

Garnish: Garnish with crushed Fruity Pebbles.

Serve or Chill: Serve immediately or chill for later.