Spread about 1 tablespoon marshmallow fluff evenly onto 1 side of each graham cracker square.
Melt chocolate in top of a double boiler over simmering water, stirring frequently and scraping down the sides with a rubber spatula to avoid scorching. Cool chocolate for 1 to 2 minutes. Spoon chocolate into a piping bag or a plastic bag with a corner snipped.
Pipe chocolate in the shape of a spider web onto the marshmallow fluff of each graham cracker. Put a dot with some legs in the corner to represent a spider.
