- You may be looking for Einarr, nicknamed "Chuckles" by the Doctor.
Chuckles and all Earth robots of his generation were products of Alistair Gryffen's genius. Before Gryffen's thought matrix allowed a robot to think for itself, robots were little more than windup toys. Chuckles had a partner, Boris, with whom he had been a clown at the circus. Balloons were his act and kids loved it.
They were taken by Freddie Maxwell to be gladiators to fight in Crashclub. Freddie thought Boris one of his best, a real contender. When K9 Mark 2 went undercover to take Freddie down, his crate was taken to the gladiator pens. Chuckles introduced Boris and himself to K9.
They soon met the champion, Pain-Maker, whom the clowns feared. Chuckles and Boris were excited K9 was their new roommate and showed him around the place, but the walls were the only interesting feature. K9 watched Boris blow up a balloon, let the air out and then repeated this action over and over. Chuckles explained that balloons were his act in the circus.
Freddie called Boris on the intercom, to go into the ring and face the Pain-Maker. The Pain-Maker tried to strike Boris but he evaded the attacks acrobatically. However, he couldn't hold out forever. The Pain-Maker destroyed him. Freddie was shocked.
Thorne was behind the scheme and made K9 face the Pain-Maker. He had the Pain-Maker flash Boris' ascot to taunt K9 into destroying the him; he was laced with the explosive solarmite so Thorne could take K9's regeneration unit. K9 was angered, but refused to fire, He escaped the Pain-Maker's self-destruction. Freddie was put out of business and Crashclub was closed down. Boris was soon rebuilt with a new pink ascot and a honker. Chuckles and he called K9 to thank him for shutting down Crashclub and Chuckles cheerfully informed K9 that he and Boris were going back to the circus. (TV: Robot Gladiators)