There was a time early in the development of the Super Nintendo (SNES) where the new console was to feature backwards compatibility with NES games. The solution would have required a cumbersome cartridge adapter and a hard switch on every console to flip the CPU into 8-bit mode. Unfortunately, it was not meant to be — outside of the first public demo of the console, little evidence exists to suggest the gamers would have been able to supercharge their old NES carts on their Super Nintendo.
This is a companion discussion topic for the original entry at https://hackaday.com/2023/12/24/nes-classic-metroid-ported-to-equally-classic-super-nintendo/