Cars 2 was the first Pixar film to feature Mater as a central character in an international spy plot.
In the sequel, Mater travels with Lightning McQueen to the World Grand Prix. After being mistaken for an American spy, he becomes involved with Finn McMissile and Holley Shiftwell in a mission concerning a plot against the race and an alternative fuel called Allinol.
This approach differs sharply from the original Cars, which centers on McQueen's forced stay in Radiator Springs and his personal growth. Cars 3 returns the emphasis to racing, McQueen's career, and his relationship with Cruz Ramirez.
Mater appears in the original film and remains important across the franchise, but Cars 2 is the installment that turns him into the main comic-spy protagonist. Planes is a separate animated film set in a related vehicle-themed world, not a Cars sequel.