When I was a mechanic in the Navy, we were on a work barge while the ship was being overhauled. The electricians were in the room next door and they had a siren they would plug in every morning at 8:00 am. We were not happy with the electricians as they had cut the plug off of our coffee pot when it kept blowing a fuse.
So I wired up a second male plug (in parallel with theirs) - they plug theirs in, I plug mine in. Siren starts. They unplug theirs, siren does not stop. A lot of confusion and then "hey shut that thing off". Great fun for us.
But later it was pointed out how dangerous this was.
Like I said I was just a mechanic. Well a nuke if you know what that is.