Yeah, a game genie'll do it for you on SNES. A Game Shark will play just about anything on Dreamcast, and the N64 Game Shark works as well, though the only really popular imports on N64 were Sin and Punishment and the Evangelion action game on it (Animal Crossing debuted there as well, but there's no reason to play that in Japanese on an older system other than to satisfy curiosity). A game genie will take care of most Genesis games, or just a Genesis 3 has a wide enough cartridge slot for anything. 3DO games are entirely interchangeable (no one cares, and with good reason), as are any Game Gear, Game Boy of any variety, and DS games. NES games simply require a cartridge converter, which you can buy easily or just rip out of an old copy of Gyromite by popping it open. A game shark will do any non-RAM upgraded Saturn games, but a 4-in-1 RAM cart is the way to go to play anything. Turbo Grafx CD plays imports out of the box provided that you have the appropriate system card, but the HuCard games require either a conversion card or an entire Japanese system. PS2 has crappy mod devices, and you're best off just buying a Japanese system. Master System's entirely interchangeable. I'm leaving more out, but maybe that's a little helpful, mobiusclimber.