Use tubed black icing to pipe the letters "RIP" onto cookies (Note: Use a toothpick to shape icing). Set aside.
Spread 1/2 in. (1 cm) band of frosting around outer rims of serving glasses. Over sink, sprinkle about 1 tbsp (15 mL) cookie crumbs onto frosting. Set aside.
In large cup, pitcher or blender, mix sherbet and milk together until smooth. Pour into serving glasses. Spray a mound of whipped cream on top of each milkshake. Sprinkle remaining cookie crumbs on top to look like dirt. Insert gummi worms over rims. Insert "tombstone" cookies into "dirt", propped against gummis.