1. Melt butter and marshmallows in the microwave until melted. Stir in Rice Krispies until well combined.
2. Lay half in the pan and press it down. Top with a layer of oreos and peanut butter cups on top of the oreos. Spread remaining Rice Krispies mixture on top. Lightly wet fingertips to help spread them. Seal the sides with Krispies too and freeze 10 mins. to harden.
3. Cut into squares. Decorate tops with melted chocolate and add chopped oreos and peanut butter cups.