Prepare a flat surface with wax or parchment paper.
In a large pot, melt butter over medium heat. Add marshmallows and stir until melted. Stir in a few drops of brown food coloring if a dark brown spider color is desired.
Remove pot from heat and add Cocoa Krispies, gently stirring until they are well coated.
Coat your hands in non-sticking cooking spray or butter. Scoop out about ¼ cup of the mixture at a time and roll / press in your hands to form a ball. Set balls on prepared surface.
Press 2 eyes into the front of each ball.
For each ball, break the 2 large arched parts off of 2 pretzels to create the legs. Use a toothpick or skewer to make holes in the balls and gently press the pretzel pieces into them. If necessary, squeeze gently to secure the pretzels in place.
Notes
If the Cocoa Krispies mixture becomes too hard while you are still making your spiders, simply microwave it for 15 seconds or so to soften it back up again.Store in an airtight container at room temperature for up to 2 days.