In a large saucepan over low heat, melt the chocolate and peanut butter chips, the marshmallows and butter, stirring constantly. (This may also be done in the microwave, using 15 to 20 second intervals just until everything is thoroughly melted.) Remove from heat. Add the vanilla and the cereal and mix gently but thoroughly. Working quickly, drop the mixture by tablespoonfuls onto waxed paper, shaping to resemble the body of spiders. While spiders are still soft, press two candies on top for the eyes and gently position 4 "legs" on each side using the chow mien noodles. Cookies will harden as they sit. Allow to sit until firm enough to move and retain their shape. Serve on platters as part of a Halloween spread.

Cookies will keep for up to several days stored in an airtight container and layered on wax paper.