MELT butter over low heat on stovetop. Add marshmallows and stir frequently until melted and smooth. Remove from heat. Stir in JELL-O powder; mix well. Add crispy rice cereal and mix until ingredients are evenly dispersed.
WITH buttered hands, take small amounts of the cereal mix and form into balls. Place on waxed paper to cool.
TO turn pumpkin treats into Jack-O-Lanterns, use little candy pieces or decorating gel, melted chocolate, licorice strings, gumdrops, etc.