I'm not going to try to explain the "why" of this... The idea has been bumping around in the old rock tumbler for ages now. They sell dolphin cookie cutters at Sur La Table for $1 and I took some pliers to one to make it m'orca.
Melt some dark chocolate chips or candy melts in the microwave at 50% for 30 seconds, stir and continue to microwave at 50%, stirring at 15 second intervals. Spread some on each graham cracker as glue, then adhere a marshmallow.