Twin Signal

It follows the story of a humanoid created by a robotics expert named Dr. Otoi for his grandson, Nobuhiko. But in the process of writing and applying the programming, an unfortunate mishap takes place! Nobuhiko sneezes. Now, whenever Nobuhiko sneezes, the humanoid (named Signal) transforms from a temperamental adult robot into a chocolate-loving baby version of himself.

Despite this little error, the days spent with the Otoi crew are usually fun. Animals, people, and robots all can live in harmony.

Until one day, Signal is attacked by Pulse, a robot created by Dr. Otoi some time ago. Much like a prototype for Signal. Pulse is incredibly nearsighted, but makes up for what he lacks in vision with firepower. Dr. Otoi's mysterious rival has packed him to the brim with amazing weaponry, with the intent of stealing the Doctor's most recent robo technology.

(Source: Wikipedia)