Pour the cold milk into a large mixing bowl, then add the instant chocolate pudding mix.
Crush 6-8 chocolate sandwich cookies into small pieces, either in a food processor or by hand in a sealed bag with a rolling pin. Fold the crumbs into the pudding mixture so every spoonful has that classic "dirt cup" crunch running through it.
Divide the pudding mixture evenly among 6 small bowls or clear plastic cups. Fill each one about three-quarters full, leaving space at the top for the whipped cream "head" you'll add later.
Place the filled cups in the refrigerator for 5-10 minutes. This short chill firms up the pudding just enough to hold its shape when you start decorating on top.
Once chilled, top each cup with a generous swirl of whipped cream or Cool Whip for the head. Add two candy-coated chocolates for eyes, then tuck two cookie halves into the whipped cream for ears or horns. Serve right away and watch the monsters disappear.