A person once saw a power cord with a plug on both ends of it and said that this was dangerous. He said it would be dangerous if both plugs were plugged in and switched on. If there were two plugs on a cord and it they were both switched on, theoretically what would happen?
It all depends, if the cord connects the 2 ‘hot’ leads to each other and the 2 ‘neutral’ leads to each other, nothing should happen. If it is switched around, and it connects the 2 hots to the 2 neutrals, all hell will break loose. You’ll probably trip a breaker or two right quick, but there may be lots of sparks (especially when you plug it in) or a fire or some other nastiness if it takes too long for the breaker to cut the power.
This of course assumes both outlets are in phase. But if outlet A was getting its hot from leg 1, and outlet B was getting its hot from leg 2, then all kinds of fireworks would occur, even if the hots were tied together…
The real danger is that if you plug one end into the socket, the plug on the other end will have voltage on it. It’s too easy to touch it by accident and get electricuted. Even if you don’t touch it, if you let the plug touch a grounded piece of metal it will cause a short circuit.
…and, um, I do know how to spell ‘electrocute,’ really.