T.R. Chula was the secondary antagonist of An American Tail: Fievel Goes West, his name is a play on his species - namely a tarantula spider and he had the appearance and mannerism of an Old West outlaw.
T.R. Chula was also sadistic and cruel, 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 terrorising mice, which he also apparently found suitable food as he threatened to devour Fievel on several occassions.
T.R. Chula would meet the same fate as the rest of Cat R. 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 - though he returns as one of the reccuring villains in the short lived television series based on the movie.
Fievel's American Tails
T.R. 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 movie. He simply serves the role as the generic unintelligent sidekick found in most Saturday morning cartoons. Appearance-wise, he goes from being gray to blueish-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.