Spray a mini muffin pan with non stick cooking spray.
In a medium saucepan over low heat, melt the butter and marshmallows, stirring frequently.
When the marshmallows are melted, stir in the vanilla and cereal. Turn off the heat, but leave the pan on the stove to keep warm.
Drop in the food coloring until the desired color is reached.
Using buttered fingers, press the cereal into the mini muffin pan. When the pan is full pop the bites out onto a silicone mat or parchment paper lined sheet pan. Repeat until all the monster bites are formed.
Decorate the monster bites with the candy eyeballs and sprinkles as desired.
Keep in an airtight container.
Candy eyeballs and Halloween sprinkles can be found at grocery stores, specialty stores and Amazon.com.