Originally Posted by plunet

The act of trying to pool power from multiple seat sockets is just dangerous and against electrical codes and liable to end up dispensing an electrical shock. I posted a link to a flippant way of cooking a frankfurter yesterday but your reply makes me suspect you are actually seriously thinking about this.

Let's have a think about it... You would effectively need to have a 4 headed cable.... 4 male plugs all joined together at some point leading to a female plug or directly to the appliance.

The problem here is that when you plug in the cable into seat 1, the protruding prongs on the plugs on cables 2, 3 and 4 are now live/hot. Add a bit of unexpected turbulence or someone misjudges things and that's someone who is now in need of medical attention. You could probably do something to mitigate this with inline switches but they would need to be double pole (both live/hot and neutral) and ideally switching all 4 cables at the same time. These kind of switches do exist but typically only for commercial/industrial applications.

Another issue is that you or I don't know the detail of the aircraft electrical supply. Most importantly is whether the supply to these different seats are all in phase with each other. If they are not in-phase then you would likely end up with some kind of kaboom when connecting sockets together that have different phase supplies. Whilst I am sure there are RCD/GFIs deployed on these circuits, you just don't know how it's all going to react. Joining together AC circuits from different phases always has a bad end result. Any other devices on the same circuit will also see an electrical surge and over-voltage situation and you might now blown other passenger devices and depending on the electrical blast radius, maybe also impact other stuff.

A different issue is that although the inferred supply is 125W per seat, you can also assume that there is some circuit and power protection for multiple seats, and it's highly likely that should all these sockets you are targeting be on the same protection device, the device would be rated lower than the maximum theoretical rating of (say) 500W. Exactly what the margins are here it's impossible for me to say. Assuming there was any sense in this idea (which there isn't) you would not be trying to target the full rated power draw through any one circuit so this would suggest that adding a 5th seat supply would be sensible. Which of course it wouldn't be for other reasons.

This is so dangerous from an electrical point of view, I wouldn't be surprised if this was discovered and there was any smell of anything having gone wrong (let alone a whiff of a hotdog) I wouldn't be surprised if you were not slapped with a lifetime ban, and that just assumes it didn't cause a problem where the aircraft didn't have to divert due to a medical emergency arising from electrocution, or being met at the aircraft door by Her Majesty's Constabulary (or other equally fine local law enforcement) due to high-flying stupidity and probably something along the lines of endangering an aircraft.

Just stop. Stop now. Pranks are all very well but safety is not something to risk at 30000 ft.