Mix the chocolate pudding powder with cold milk according to package instructions, then whisk until smooth and set in the fridge to chill for at least 30 minutes.
Crush the Oreos into fine crumbs using a rolling pin or food processor, leaving some bigger pieces for texture.
Spoon a generous layer of chilled pudding into each clear cup, filling about one-third of the way up.
Sprinkle a thick layer of crushed cookies over the pudding to resemble dark soil.
Place gummy worms and candy skulls on top of the cookie layer, burying some slightly into the crumbs for a realistic effect.
Cut shortbread cookies or biscotti into small rectangles to serve as tombstones; use icing or melted chocolate to write spooky messages if desired.
Insert the tombstones into the crumb layer, standing upright, and pipe whipped cream around their bases to resemble fog or mist.
Sprinkle edible glitter or colorful sprinkles on top for shimmer, then chill the cups in the fridge for 15–20 minutes to set everything.
When ready to serve, ensure the toppings are firm and decorations are stable. Serve chilled for a fun, spooky treat that looks just like a mini graveyard.