J. Curby Gremlin is a red-violet Gremlin with yellow hockey stripes who works for Professor Z. He is head of the Gremlin family. During the film, J and the other main heads of the lemon families (Pacer, Trunkov, Hugo) attend a meeting with Professor Z in Porta Corsa to discuss their evil plans to discredit Allinol by using the radiaton disguised camera to crash out the racers in the World Grand Prix that use it, ensuring that all cars keep using conventional fuel to secure the profits of their "lemon" organization who managed to secure the largest unexplored oil resources in the world. J. Curby is seen smiling at the idea.Near the end of the movie, he is sprayed with a strong stream of water by Red and is arrested in London with fellow lemons.
- He is the only head lemon seen with a weapon.
- He doesn't appear in Cars 2: The Video Game - Don Crumlin does however.
- In Cars 2, he mentions that he is from Detroit, Michigan.
- He acts tough, but he secretly loves to watch musicals.
- He was once maitre d' at the flagship restaurant of superstar chef Motorio Brake-tali. These days, J. Curby has turned to a life of mischeif, serving up danger and singing a more ominous tune.
- J. Curby is a 1975 AMC Gremlin.