rule

People want them around the holidays because they hang their lights in the wrong direction and end up with 2 female plugs where they needed one to be male.... So the want the danger adapter because they are not wanting to take anything down

I absolutely do not consider that to be a sane reason.
- Nope should anyone.
That happens tooooooooo
Then doesn't that just make a closed loop with no power?
- So someone wires up lights around a bush or tree and one side ending in a socket is powered correctly. But they fucked up and the line to connect to it is flipped; it isn’t a pronged plug but rather another socket.
  
  So instead of rerunning that flipped line of lights, they go cut two extension cords to create The Naughty Plug and use it to run power from the powered socketed plug to the unpowered socketed plug, leaving an energized prong plug vibing somewhere at the end of the line ready to maim, murder, or incinerate someone.

You can run something like a house off a generator with one if the main breaker is off; in an emergency and the operation reasonably well planned out (don’t overload wall lines you plugged into, etc.) it might be a net benefit. On the reg is asking for death cause there’s safe ways to do it that sane people would plan for on the reg

That would surely only power a single circuit (due to isolation) and if you have to be selective, a critical circuit like your fridge isn't really likely to have a wall port on the same circuit near where you'd happily have your fume emitting generator..

I'm no electrician but I've generally installed automatic transfer switches (ATS) for mine site server cabinets that then power UPS racks and the transfer switch automatically or manually can switch from mains to generator if mains power goes out (which at a mine is all the time). I feel like a similar and safe system must exist for homes. Or something no different to switching solar to grid and back.

But again, not an electrician.
- In your typical household panel there is no isolation. If you're lucky there's a GFCI for the bathroom and kitchen.
  
  Edit: not to imply GFCI provides isolation either
  
  Which is insane to me. RCDs have been required on all household circuits for decades in Australia. Literally saved my life when I was doing dumb shit as a kid.
  
  Edit: Also, by typical, you mean a typical American household :P
  
  I was thinking British, but my understanding of the technology you mentioned I don't see any clear reasons why it would prevent back feeding?
  
  It didn't. The mains was on, and the plug was in my hand. My dad, in a typical show of his wonderful parenting, told 9-year old me to plug it in while he went outside to the fusebox to turn the main circuit off. The power came back on while I was walking out to the back shed. I still got a pretty big zap, in the eyes of a kid anyway.
  
  Wait so, if your kettle fails, your fridge loses power for example?
  
  In Murica, the kettle tripping a circuit breaker would knock out the fridge if the fridge was on that breaker circuit. Anything not on that circuit breaker is fine.
  
  No isolation here just means that if the breaker doesn’t trip, the kettle’s circuit and fridge’s circuit are connected together in the circuit breaker box by copper bars.
  
  Ah yep that makes sense though I'm following now
- Circuits are connected to the circuit breaker, so it would power whatever is on the breaker. (Or more precisely, whatever is on that leg of the hot.)
- If you disconnect the mains then the power will be backfed through one of the circuit breakers and back out to others. If the breaker you plugged naughty plug into is off, it’s isolated. Otherwise, it’ll power whatever circuit breakers are on on the breaker panel.
  
  If you don’t disconnect from the mains you’ll kill a person working to fix the electrical lines for your neighborhood.
  
  Yes, safe and automatic things exist to switch automatically - or even hook up a generator in a pinch manually but safely (no naughty plug needed).
  
  Defo don’t backfeed your abode unless you’re gonna die due to some major emergency!
  
  Oh okay, I see.. Or rather, I see I don't understand lol
  
  That’s fine, electricity is weird! I stay away from naughty plug because if you do everything just right you’ll live another day, if you do anything wrong you’ll kill yourself or someone else. Saying no to naughty plug should be sufficient for you too ;)
  
  Wires don't have a direction

At work, I have a freezer with a couple thousand dollars of product in it. If I lost power and only had male plugs to jerryrig the generator into the circuit, I would. BUT only after turning the mains off and padlocking the panel shut. I didn't have to do that as I just wired the generator directly to the freezer after disconnecting it from the mains.

Wait, an electrical outlet can be an inlet too?
- Mains outlets aren't smart, they're just wiring with contact points. If you feed power into an outlet, it'll energize the circuit it's on, which is a bad idea if your mains circuit breaker isn't off.
- Technicaly it is connected through the breaker so you could only supply as much to the rest of the house as that breaker can pass. Not ideal or the proper way of doing it though. Also the reason to disconnect from the grid is that you could start feeding downed power lines, and if line workers go out to work on the lines they can be electrocuted. Also, theres no telling when power will return. There should be a separete input for the generator and a transfer switch to switch between the generator and grid.
  
  There's a reason why home battery storage systems needs to be connected to the breaker panel. You route power through it. When the batteries aren't needed then it's just a dumb relay for grid power. When you're drawing power from batteries it disconnects the grid.
  
  Only a few industries ever draw power both from grid and local power sources at once (during peak load) and they route all the power sources through a power distribution system which prevents backfeeding.
- Yes. It's called backfeeding I believe.
- Any outlet can be an inlet if you are daring enough (don't do it with water mains though)

Hooking a generator into your house wiring in an outage. One end in the generator, one in a spare wall plug.