Zed is the name assumed by a robot created by Dr. Lieter Greenbox. Originally designed as a micro-brain repair unit, the Metallikats used it to repair their badly-damaged bodies. Its programming became infected by their personalities, and it became sentient, taking the name Zed and following them around. It assimilated metallic components nearby to create armor and weapons for itself. It soon grew tired of the Metallikats' lowly ambitions and sought to find its own purpose in the grand scheme of things. When Mac tried to get control over it, it became angry and assimilated him, to Molly's horror. The Enforcers tried to stop it, but it assimilated their tanks and weapons. Even the Swat Kats were unable to defeat it on the first try, and had to retreat. Zed headed for Puma-Dyne to assimilate the weapons being made there. The Swat Kats, with Dr. Greenbox and Molly's cooperation, took on the robot again, but it assimilated Molly and fused with Dr. Greenbox, deluded into thinking that its purpose was to help its creator conquer the city. The Swat Kats destroyed the micro-brain just before it would have nuked Megakat City.
Zed was voiced by Charlie Adler in the original English version and by Tomomichi Nishimura in the Japanese dub, and this character appeared only in the episode "Unlikely Alloys."