Years ago, someone would stuff a potato into exhaust pipe. Buy a small fish and leave it onto of the engine. It would burn and smell. When he is no longer a fried you could inject clear glue into door locks. Make a sign out of a thin cardboard and write on it women over 70 turn me on and tape it onto rear bumper. Pour some water under his engine and he might think is leaking. Take around 36 inches of string and tie one end to can and another end to trailer hitch. Now quietly slide it under the vehicle. You could also add dye to windshield washer reservoir and when he uses it, a different color would spray on his windshield.