Famicom Disk System. A pretty revolutionary approach, from a time when nobody thought people would care about old games just a few years down the line. You could erase your Zelda or Metroid disk to write something on it that's totally obscure today. It's incredible what we managed to preserve from that time, considering that some less successful games risked getting completely obliterated from those disks to make place for the best ones.
Then Nintendo realized their games would actually hold their value throughout the generations, and here we are, wondering if we'll have to rebuy some Switch games at full price.