TARS is one of four former U.S. Marine Corps tactical robots along with PLEX, CASE and KIPP featured in the Interstellar universe. He is one of the crew members of Endurance along with Cooper, Brand, Doyle, Romilly, and CASE. TARS' personality can be characterized as witty, sarcastic, and humorous, traits programmed into him to make him a better suited companion. TARS also appears to be somewhat more versatile than CASE, being suited for tasks ranging from piloting to data collection.
TARS is voiced by American actor Bill Irwin who also operated the hydraulics of the robot. He controlled the heavy machinery which weighed almost 200 pounds. The actor was digitally removed during post production as he was a few inches taller than TARS.
TARS spent 23 years maintaining the Endurance along with Romilly. In a cruel twist of fate, he was also a witness of Romilly's death when a booby trapped KIPP exploded.
TARS joined the crew and notified them of Romily's death. They rescue Cooper and chase after the Ranger with Mann inside. Mann intends to dock the Ranger with the Endurance and strand the crew on his planet with no supplies, but TARS manages to foil his plan when he reveals he has disabled the automatic docking routine on the Ranger as he did not trust Mann. He later helps the Lander dock with the rapidly-spinning Endurance after Mann dies.
TARS was then shot into the Gargantua black hole to collect quantum data that could save humanity by solving the issue of gravity, as well as to help the Endurance out of Gargantua's pull. TARS gets lost inside the tesseract along with Cooper, but manages to contact Cooper and tell him about the Tesseract. They are both discovered by Rangers floating in space after their encounter with the Bulk Beings.
Cooper reprograms TARS at his old farmhouse orbiting Saturn before they set out to find Brand on Edmunds after they steal a next-gen Ranger spacecraft.
With this, TARS is one of the four surviving crew members from the Endurance, along with Cooper, Amelia, and twin robot CASE.
Despite being a robot who follows the order of his crew, TARS is quite intelligent and is capable of acting on his own. He suspected the possibility of Mann betraying the crew and disabled the auto-pilot to prevent Mann from stealing the Endurance.
In the original script, TARS had a more human-like appearance, but essentially the same personality and lines and is still 90% honest.