The professor is a minor character in Splatoon and Splatoon 2. He was a human who lived 12,000 years before the events of the games. He was both Judd's original owner and the creator of the AI Tartar. Not much is known about the professor, other than the fact that he was rather intelligent, and that he loved his cat.
In Splatoon, two Sunken Scrolls feature writings from a concerned pet owner. Worrying about the lack of action being taken by "the policy makers" in regards to the Earth's rising sea levels and the wellbeing of Judd, the professor had him cryogenically frozen for 10,000 years. In Splatoon 2, another Sunken Scroll reveals that the machine Judd was enclosed in could produce a clone of Judd. The pet owner appears to be remorseful over the process of preserving Judd and ensuring he has company when he wakes up.
In the Octo Expansion, Commander Tartar states that it was created by a "brilliant professor" to pass down humanity's knowledge to the next "worthy" lifeform in hopes of rebuilding civilization after the extinction event.
In a Famitsu interview with the game staff, director Yusuke Amano confirmed that the pet owner and Tartar's inventor were the same person and that the professor's intent in programming Tartar was for the next intelligent lifeform to not repeat the mistakes of the human race. However, Tartar's loneliness caused its programming to disregard its creator's original intentions as time went on. Yusuke Amano also said that the model in F07C12Matchmaker Station is based on Judd, and that this is supposed to be an in-game hint that Commander Tartar has some connection with Judd's owner.[1]