R.O.B. (short for Robotic Operating Buddy) was an accessory for the NES. It was designed for usage with the NES, and was compatible with only two games: Gyromite and Stack Up!.
Although only 2 games were compatible with this NES accessory, it played a much larger marketing role. After the 1983 North American video game crash, retailers thought that home consoles were dead, and when Nintendo presented the NES, nobody would buy it. However, by using R.O.B. and other accessories such as the NES Zapper, they convinced retailers that the NES is a toy, not a videogame console.
An individual R.O.B. appears as one of the new, unlockable playable character in this installment. In The Subspace Emissary, this R.O.B. is the true identity of the Ancient Minister, the commander of the R.O.B. forces.
Like in F-Zero GX, R.O.B. appears in the background of the Port Town Aero Dive stage.