Heat the butter over medium heat in a large pot. Once melted, add your regular marshmallows. Remove from heat.
Add in the cereal and Lucky Charms marshmallows. Stir to combine.
Place on a well oiled 13 x 9 x 2-inch pan coated with cooking spray or wax paper.
Let cool then spread evenly on the pan. Cut into squares and serve! I like them warm, but you can refrigerate them if you want them less "gooey."