Sergeant Sirius is a character from Loonatics Unleashed.
Based on Commander K-9, Sergeant Sirius is Melvin the Martian's dog. Unlike K-9, Sirius is a robot since he can fly. His first name is probably a reference to Sirius, the so-called dog-star (it should be noted however that Sirius Black's first name is derived from the same source). It is possible that Sergeant Sirius is not a descendant of K-9 because K-9 was a living dog and Sirius is a robot, so it is possible they are not related except for appearances. He could be a possible cyborg but this is never confirmed.