Put almond bark in a small crockpot and cook on low for 1 hour. Add peanut butter and stir until melted and combined.
In a large mixing bowl, combine cereals and marshmallows. Pour the almond bark mixture over top and stir until everything is well coated. Work quickly so the marshmallows don't melt competely.
Drop heaping tablespoonfuls onto wax paper. Let set completely.