When Atari decided to release a sequel to Asteroids in 1980, they added several new features to the existing game, and called it Asteroids Deluxe. Unfortunately for the company, the sequel was not a hit, and most would-be fans opted to stick with the original Asteroids. So, when Atari wanted a sequel to Centipede they knew they better try a different game plan. This time, they added several new features to the existing game, started to call it Centipede Deluxe, but then changed the name to Millipede before pushing it out the door.
The change apparently paid off, since Millipede enjoyed at least a little more success than Asteroids Deluxe did. Centipede's popularity was not displaced any more than that of Asteroids had been, but Millipede did well enough to warrant several home conversions, including ports for the Atari 2600 and the Nintendo Entertainment System. So, while Centipede remains the better known of the two, Millipede became the little sequel that could.