Robo-Chief was a robot in the first Dog Man book, appearing in Chapter 2: Robo-Chief as the secondary antagonist.
Biography
In Dog Man, the city Mayor warns Chief to keep watch of Petey and make sure he doesn't escape or he will be replaced by a robot, referring to Robo-Chief. Dog Man follows the Mayor's footsteps to the Robo-Time Industries where he sees the Mayor with Dr. Scum, inventing a horrible robot to use to take over the city.
33 seconds later, in Cat Jail, Petey receives a can of Invisible Spray from the mail. Petey sprays himself and breaks free. The police headquarters get a call from Cat Jail to tell them that Petey escaped again. This leads to the Mayor firing Chief, and sending in Robo-Chief to be in charge.
Later on, it chases after Invisible Petey and firing missiles missing and hitting all of the rotten business stores. Then it is destroyed after firing a missile through a corkscrew slide, which backfires. The missile hits and him, making Petey get away.