Tow Mater (More commonly known as Mater) is an anthropomorphic tow truck who first appeared in the 7th Pixar film, Cars. He, unfortunately, got flanderized after he became the protagonist of the 12th Pixar film, Cars 2.
The role of protagonist doesn't belong to Mater, it always belonged to Lightning McQueen.
Instead of being just a tow truck, he was reduced to being a (poorly executed) spy.
He gets overly excited when seeing Lightning return, which wouldn't be a problem if he didn't keep bonking Otis into the road.
Mater can also be seen disturbing other vehicles such as trains, dump trucks, etc. at Radiator Springs at the beginning of the film.
He also wants to befriend foreign cars just because he saw them on TV, and he is excited to see them in person to the point it gets annoying really quick.
He even made McQueen lose the Tokyo race. Despite of losing the race, it was truly an accident.
Mater became more of a dimwit than he was, but not in a good way unlike how he was in Cars and Cars 3.
His personality is inconsistent throughout Cars 2: some scenes show him being smart and providing Finn and Holley with useful info, but the movie backtracks sometimes to show him doing dumb things, like interrupting the traffic in Paris and making fun of the royal guard in London.
He redeems himself in Cars 3, giving the support McQueen needs whenever he feels down.
There were some funny scenes involving him, like where he went into the girls bathroom and mistaked wasabi for pistachio ice cream.
He did a nice job as a spy, figuring out that Miles Axlerod was behind the alternative fuel conspiracy.
He does live up to his first line in the movie: "Mater, Tow Mater, Is HERE to help ya", since he actually helped Otis, Finn, Holley and Lightning (at the final moments of the film).
While the scene where he has hallucinations failed at being emotional, it may have made the fans feel sympathetic at him (not all of them, though)
He's aware of his mishaps.
Larry the Cable Guy still gives a good performance.
The Cars franchise wouldn't be the same without Mater.