My cousins did this to me as a kid. I thought it was great that a little battery could give such a huge jolt simply reversing the input side of a step down transformer to the output side.
As kids we had rudimentary knowledge of what a transformer did since our country used 220v but most of our electronics came from the U.S. and needed a step down transformer.
...and it really is a pretty good jolt if I remember correctly. After reading this post I considered rebuilding my project and showing it to my wife....but that's probably a bad idea lol.
