Yellow robot

A yellow robot was sent to Earth to find the heir to the throne of its planet. Along with a red robot, it removed all the humans, apart from those that were "grounded" by the Judoon, from Earth while they searched. The heir, a half-human called Gavin, was hidden by a bio damper. When removed, the robots recognised him. They returned the humans and took Gavin home. (TV: The Empty Planet)