Which actor was famous for supposedly using the catchphrase "You dirty rat!"?

James Cagney (1899 - 1986) is the actor who never actually uttered the phrase “You dirty rat!” in the 1932 movie "Taxi" or in any other, but it is often used as a supposedly typical Cagney movie quote/misquote. When the phrase is used it means the rat is a person who is deemed to be despicable or contemptible. In the movie, the closest Cagney got was: “Come out and take it, you dirty, yellow-bellied rat, or I’ll give it to you through the door!”

Cagney noted that he believed film studio executives acted like rats. He faced them and got into hot water. He made a decision to take on studios’ powers to demand higher salaries, even though he was already one of the best-paid names in Hollywood, CA. He was matter-of-fact about his attitude, saying, “I walked out because I depended on the studio heads to keep their word on this, that or other promises, and when the promises were not kept, my only recourse was to deprive them of my services.” He came back when the studio offered "Angels With Dirty Faces" (1938); he was eager to do the movie.

It was said, "In real life, Cagney loved the kind of ambiguity associated with the true about real quotes and misquotes. He seemed to have fun when asked countless times about the catchphrase 'You dirty rat!', never revealing the truth on if he ever said it on any occasion."

Cagney had the type of persona that made him a real iconic actor; he actively made films from 1919–1984.