H
HavBlue
How much damage does that do?
When the vehicle is put in reverse it triggers the lamp and because the drops of gas have evaporated it causes a very quick flash fire that blows out the bulb with a bang but doesn't hurt the taillamp lens. Remember, we're talking small drops here as we are trying to make a lot of noise without damaging anything other than the bulb.
Now, you want a really big bang try a spark plug sealed in a 1 gallon anti-freeze bottle cap that is wired to the coil. The bottle is filled with 1-2psi of Acetylene oxygen and it can be rested in the wheel well. When the ignition turns the engine over "big boom" and old Harry, rest his soul, pissed his pants "literally" on that one. Harry was a prankster himself and trust me, he gave as good as he got.