He was voiced by Tom Kenny.
In "Copue D'Etat", Professor Utonium got bit by the shopping bug, while strolling through an auto shop and bought himself a ton of parts for his car. He completely tricked it out and turned it into a super high-tech, fully functioning smart car, appropriately titled "K.A.R.R.", which stands for "Kinetic Automatic Robotic Roadster".
Professor Utonium showed off all of K.A.R.R.'s amazing new features to The Powerpuff Girls, and blew their minds with all of the things it could do, especially, the fact that it could talk and interact with them. K.A.R.R. erroneously called them "The Powderpuff Girls", and Blossom corrected him, but K.A.R.R. condescendingly laughed at her. Buttercup said that they should go for a ride in K.A.R.R., but Professor Utonium broke to The Powerpuff Girls, that K.A.R.R. was only built to seat one person and he drove off in K.A.R.R., leaving The Powerpuff Girls alone for a long time.
The Powerpuff Girls got sick of how Professor Utonium was spending too much time with K.A.R.R. and not enough time with them, so they poured some engine stop into his engine, but K.A.R.R. was immune. So, he got mad at The Powerpuff Girls and attempted to run them over. Professor Utonium caught him in the act and knew it was time to get rid of K.A.R.R. and revert him back to normal, first thing tomorrow.
The following morning, Professor Utonium was kidnapped and tied up inside of K.A.R.R. and The Powerpuff Girls needed to save him. They fought with K.A.R.R., but it was not an easy task, as K.A.R.R. was equipped with so many features. Plus, if they did anything to K.A.R.R., they would end up hurting The Professor. Eventually, The Professor hit the ejector switch on the dashboard and launched himself to freedom and The Powerpuff Girls were given the go to destroy him, but when they were about to finish him off, K.A.R.R. started crying tears of oil and told them that he was just jealous of The Professor spending more time with The Powerpuff Girls, than with him. The Powerpuff Girls understood how he felt, so they appealed to his humanity and let him live.
Professor Utonium came up with a win win solution, that would suit all of them. He constructed a robotic version of himself, named "P.R.O.F." or (Person Replacing Original Father), who would drive in K.A.R.R. non-stop, and allowing K.A.R.R. to be happy with a robotic version of The Professor, and allowing the original Professor to devote more time to his girls. P.R.O.F. drove off with K.A.R.R. real far, and all was right with the world. This was all until Blossom brought up the question, as to what Professor Utonium would use to drive around now, putting The Professor in a state of shock, abruptly ending off the episode.
- He could be a parody on K.A.R.R. from Knight Rider. Both of them are evil, artificially intelligent cars with the same acronymic names, despite their names being comprised of different words.
- When K.A.R.R. said "I'm sorry, Blossom. I'm afraid I can't do that.", this is the same line that HAL 9000 said to Dave in the movie, 2001: A Space Odyssey.