Place the small cup upside down on a foil-covered platter or piece of cardboard, then place the cake over the cup so that the cup sits in the hole.
Color 1/2 cup of the frosting green. With the remaining white frosting, frost the cake.
Slice 1 inch off one end of each Twinkie. Use some of the green frosting to attach the Twinkies to each other, bottom to bottom. Insert the combined Twinkies into the hole in the cake, resting the cut end on the cup. Frost the exposed end green.
Make the alien's eye by opening the sandwich cookie and pressing the Spree candy into the filling, then press the eye onto the Twinkies.
Decorate the cake as shown above. Right before serving, add the clear cup and the activated glow sticks.