Mater

Mater is a rusty old two truck and Lightning's best friend who is the secondary protagonist in Cars, the main protagonist in Cars 2 and again the secondary protagonist in Cars 3.

Cars
When Lightning McQueen wakes up in the Radiator Springs impound, Mater wakes him up and says he was wondering when he was going to wake up. Lightning told Mater to get him out but the tow truck was stopped by Sheriff, who orders him to take Lightning to the Traffic Court