Soak the tapioca in water overnight according the the package instructions. Drain.
Prepare the boxes of jello in two separate containers, according to the package instructions. Place 2-3 gummy worms or spiders in the bottom of 10-12 small cups. Spoon the tapioca pearls over the worms and spiders evenly.
Carefully pour the jello over the tapioca. Pour the green over 5-6 cups and the purple over the remaining 5-6 cups. Move to the refrigerator and chill to set, 1-2 hours until set.
To un-mold, run a sharp knife around the rim of each jello cup. Set the bottoms of the jello cups in a tray of hot water for 30+ seconds. Flip onto a plate.