I believe the method they used for the glow-in-the-dark Jell-o in the commercial was to put a light of some sort under a glass serving dish . The Jell-o itself does not actually contain any glowing properties, but acts as like a stage light “gel,” coloring the light as it passes through.
Your favorite flavor gelatin (red or green looks best), large package.
mold pan
Angel food or Bundt cake pan
Clear glass plate
Small flashlight (I am also thinking you can buy one of those small safety flash red strobe-type lights for night use…the kind that uses the AAA batteries.)
Prepare the gelatin according to package directions and pour into mold or a big plastic bowl. Take a Bundt cake pan or any angel food cake pan with a hollow cylinder center where you can insert a small flashlight. Unmold the gelatin onto the clear glass plate and place the plate atop the cake pan with the flashlight underneath, standing up. Turn out the lights! For extra special effect, you can put the blinking red strobe light under another small transparent glass dish or plastic wrap and put that under the gelatin as well.
Some ideas:
blue gelatin with red flashing strobe light
lime gelatin with red flashing strobe light
layered gelatin mold of red, green, and yellow gelatin with lights under it