In Pixar's Cars, the blue Hudson Hornet who becomes Lightning McQueen's mentor is Doc Hudson.
Doc is the town physician and judge in Radiator Springs, but he secretly has a remarkable racing history. He was a three-time Piston Cup champion before a crash ended his competitive career. His past explains both his skill and his resentment toward the racing world that moved on without him.
Lightning initially treats Doc as an obstacle and refuses to respect his advice. Over time, Doc recognizes Lightning's talent and agrees to help him prepare for the decisive race. Their relationship gives the film its central mentorship story and allows Doc to reconnect with racing on his own terms.
Smokey is Doc's former friend and crew chief who appears in Cars 3. The King is a different champion, and Sarge is a military surplus jeep in Radiator Springs, so neither is the blue Hudson Hornet mentor.