Play Gameboy Games on your NES!Bunnyboy from NintendoAge forums slapped together a custom NES cart. Packed inside is literally an entire Gameboy, from the Gameboy cartridge slot to the expansion port for peripherals like the Gameboy printers and the Gameboy light. He calls the creation "the Super GameBoy, without the Super part."
The cartridge allows one to play original Gameboy games on the NES using the custom board which translates the Gameboy graphics to NES format, and the NES controller to Gameboy format. Note that this is essentially the Super Gameboy but with a lot more custom technology in it, and it's for the NES, not SNES.
Bunnyboy says that for the moment he doesn't have any more but he's planning on building additional units in the future for a price of $130 / unit.
Source:
nintendoagehackaday