I recently watched a YouTube video on the channel Blue Television Games where they played a special kind of rom hack for Super Mario Bros 1 on the NES called Super Mario Bros. 1 & 3 Mashed Together.
I’ve run countless rom hacks with RetroArch in later years, but what’s unique about this kind of rom hack is that at its current state this kind of rom hack seems to only run on special NES emulators “on steroids” (fceux and mednafen), thereby not making this rom hack compatible with original hardware.
I know the Mesen NES emulator has got support for custom graphics in recent times, but this rom has the extension *.nesm which I suppose is a new custom format for NES roms.