Begin by preparing the chocolate pudding according to the package instructions, whisking the mix and milk until smooth and thickened. Set aside to cool slightly if needed, or use immediately if it has a soft set.
Spoon the prepared pudding evenly into small cups or jars, filling about halfway to create the base layer. Smooth the top gently with the back of a spoon for a clean surface.
Sprinkle a generous layer of crushed Oreos on top of the pudding to resemble dirt. This creates a crunchy, dark topping that looks like soil in the graveyard scene.
Place tombstone candies into the dirt layer, pressing them slightly into the crushed cookies to secure them in place and give the appearance of grave stones.
Add gummy worms slithering across the 'dirt', tucking some into the crushed cookies and letting others drape over the edges for a dynamic, eerie effect.
Repeat the layering process if desired for a taller effect, or serve immediately if the layers are complete. Chill briefly if you want the pudding to firm up further before serving.