That grey bit at the top is the Famicom-to-NES adapter (the games are the same, but NES games have more copper contact pins than Famicom games, basically)
It also has (two) controller ports so you can play two player games. But here's the fun part -- the controller ports are standard DB9 serial ports, which means you use a Sega Genesis controller instead of an NES controller!
Another interesting thing is that it does have audio/video out so you can hook it up to a TV and sue it like a regular console -- but it uses the Sega Genesis video out connector! OK!
It still works. The AC adapter power doesn't but using 6 AA batteries does. Yes, the cartridges go in backwards, something that made me waste 5 minutes and a lot of cuss words.
Here's me playing an unlicensed game (Dizzy) plugged into an unlicensed accessory (Aladdin Deck Enhancer), plugged into a handmade Famicom-NES adapter, plugged into an absolutely hacked together unlicensed portable Nintendo.
OK, I think that's all the video game (mostly Nintendo) oddities I have lying around. If I find anything else during my cleaning of closets during a pandemic, I'll add to this thread.