I hope you were diligent and brought a box of baking soda with you to clean the battery terminals of those poor unfortunate libs. Can't get a good connection if the terminals are covered in muck, you know. In fact, it would be even better if you were to use it to clean the INSIDE of each of the battery's cells - about a tablespoon per cell should do it.
You are a twisted soul.......Reminds me of the submarine commander who ordered deionized water to fill his batteries.
For automobile pranks, I prefer the ping pong ball with two small holes in the gas tank. When the car sits still, it sinks and settles on the fuel line opening, blocking the flow. After two days, it's disolved from the fuel. Right about the time the mechanic will drop the tank. Every time a towtruck moves the car, the ball rolls off the opening from being tilted and the car will start and drive. Once it's parked for an hour again, it dies.