>That time Namco released a Gamecube game that was under 500KB because it was just an emulated NES game on a disk

And by under 500KB I don't mean just the ROM and emulator, I mean the entirety of the disk. The ROM, emulator, gamecube libraries, banner graphics, save icon, everything. It still all together ended up being under 500KB. The entire trimmed disk image could fit on a floppy disk twice over with room to spare.

Course, GameCube disks were all padded to 1.4GB so literally 99.97% of the disk was padding, unless you trimmed the iso.