1. Create a model of a large tentacle using crumpled, rolled newspaper secured with masking tape.
2. Shape foil around your model to create a gelatin mold. Add enough layers of foil so that it is well supported when the gelatin is added. Arrange mold in a roasting pan so that it remains stationary. Remove model and line inside of mold with plastic wrap.
3. Add 1 box gelatin mix to a medium bowl. Pour 3/4 cup boiling water over mix; stir to dissolve. Stir in 1/2 cup ice water; pour into mold. Cover and refrigerate for 1-2 hours, until completely set.
4. Prepare second box of gelatin as noted above; allow to cool slightly. Pour into mold over set gelatin. Cover and refrigerate for 30 minutes. Peel banana and cut in half lengthwise, then into 2-inch pieces. Arrange pieces in a line the length of the tentacle to look like bones, pressing down lightly so the banana sinks to the center of the gelatin. Arrange blueberries over top of the gelatin to look like tentacle "suckers," press down gently to secure. Refrigerate for another 2 hours, until completely set.
5. Invert the mold onto a platter, remove mold, and serve.
Experiment with any fruit you like, except for kiwi and pineapple (the enzymes break down the gelatin)!