You can add wireless controller support to the NES through its unused expansion port

The NES Hub is compatible with NES consoles featuring the same design as the North American model. | Screenshot: X RetroTime has found a good use for the expansion port Nintendo included on the underside of the NES but never utilized. Its NES Hub connects to that port and adds Bluetooth connectivity, allowing up to four wireless controllers to be connected to the almost 40-year-old console.
The NES Hub is currently available for preorder through 8BitMods for $57.28 and is expected to ship as ear