I used the Sunshine game streaming software and the WiiU homebrew port of Moonlight to get game streaming working on a WiiU gamepad. It's sort of like a bootleg Steam Deck, and it works surprisingly well, but it mostly just made me want a Steam Deck.
Super deep cut (this might be my most obscure bit of Nintendo trivia as I couldn't find any images of it online), but have you ever seen the hidden wireframe models in Red Alarm? If you shoot very specific places in game, you can reveal low-poly 3D models of a Virtual Boy, Game Boy, and even a girl in a bikini... for some reason. I wonder if Nintendo's top brass were aware of that one when it shipped :-)