Melt the dark chocolate wafers (¼ cup) in the microwave on 50% power and stir until smooth. (You could also use chocolate chips or chocolate fudge for a similar effect.)
Spoon melted chocolate in a plastic bag and snip off one corner. Pipe chocolate along the edge of the cup, applying more pressure in some areas to create the dripping effect.
After chocolate hardens, use a permanent black marker (Sharpie) to draw on the eyes and mouth.
Combine mint chip ice cream (1 quart) and milk (½ cup) in blender and blend until smooth. Add drops of food coloring until it's the desired shade of green. Pour into prepared glasses and serve with a straw.