You Dirty Rat, You Killed My Brother

[Jasbird]

What is the original.

Were the lines uttered by James Cagney or Edward G. Robinson. What was
the movie called and what were the actual lines?

I vaguely remember Robinson but I'm told it was Cagney.

[Okierazorbacker]

The mobster refrain, "You dirty rat!" - was never said verbatim by
James Cagney, although he did say something similar, "Mmm, that dirty,
double-crossin' rat," in Blonde Crazy (1931). [In Home Alone (1990),
Macauley Culkin watched a scene from a fictional B/W gangster film
videotape titled, "Angels With Filthy Souls" (a take-off on the Cagney
film Angels With Dirty Faces (1938)), in which a gangster shoots his
girlfriend, while saying, "Take that, you dirty rat!"]