[Zeke]

"...male receptor on an outside wall going to a female receptor on the inside wall." is potentially a widow maker w/o a transfer switch. If you know it's not connected anything else whatsoever unless it's just a through-the-wall connection like the 2 ends of an extension cord. There are still ways you could manage to inadvertently get some back feed into your house circuits so study what you are doing. If you unplug the fridge and plug it in to your device and nothing else, you might be safe. But it has to be isolated in every way.