Bob is one of the alien twins who work at MIB headquarters. He and his twin brother Idikiukup (referred to as Bweryang in Men in Black) are often seen operating consoles and supplying the agents with information. They occasionally leave MIB headquarters and accompany J and K on missions, usually if those missions involve space travel.
Bob's species has eight arms and a single eye on a stalk.
The twins introduced the 37 hour day at MIB headquarters, which is the length of a Centaurian day. This hints that they might come from Alpha Centauri, but this is never stated anywhere clearly.