T.R. Chula is the secondary antagonist of An American Tail: Fievel Goes West, and its spinoff Fievel's American Tails, his name is a play on his species - namely a spider and he had the appearance and a mannerism of an Old West outlaw.
In the film, he was voiced by Jon Lovitz, who also played Emperor Tod Spengo in Mom and Dad Save the World, The Peeper in Little Nicky, Mr. Marks in The Producers, Artie Ziff in The Simpsons, Arthur Belt in North, and Quasimodo Wilson in Hotel Transylvania. In the TV series, he was voiced by Dan Castellaneta, who voiced Homer Simpson and other characters in The Simpsons.
An American Tail: Fievel Goes West
Chula was a sadistic and cruel outlaw, though still rather hopelessly inept at his job, he acted as the right-hand man to Cat R. Waul and enjoyed causing mischief he was also fond of terrorizing mice, which he also apparently found suitable food as he threatened to devour Fievel on several occasions.
Chula would meet the same fate as the rest of Waul's thugs, however, in the end as was fired off into the distance when their giant mousetrap was used against them, acting like a catapult and sending the outlaws soaring out into the desert.
Fievel's American Tails
Chula would later appear again as Cat R. Waul's sidekick in Fievel's American Tails. In the show, he is more tamed and nowhere near as insane as he is in the film. He simply serves the role as the generic unintelligent sidekick found in most Saturday morning cartoons. Appearance wise, he goes from being gray to bluish-purple. It is implied in the show that he only does evil things because Waul tells him to, whereas in the film he enjoys acting evil. This is best illustrated in the episode "That's What Friends Are For", when Chula becomes lonely while Waul is away, he actually attempts to befriend Tiger and Fievel, completely contradicting his characterization in the film. But when Waul returns, he decides to betray Fievel's trust by luring him into a trap, again only because Waul told him to do it.