Mr. Hyde, I presume?

As a youngster (I couldn't have been more than eight or nine), an older cousin and I lined a box with tin foil, leaving a small gap between the sides and the bottom, and wired it to an electric-train transformer. We then caught a frog and put it in the box. As long as the frog remained on the floor of the box, he was safe; if he tried to jump out, however, and his forelegs touched the sides, he completed the circuit and received a jarring jolt. (Within each of us, I fear, is a player called Hyde demanding his time on stage.)