James Cagney

Everything About Fiction You Never Wanted to Know.
/wiki/James Cagneycreator
The original Public Enemy.
"You dirty rat!"
Not James Cagney

James Francis Cagney was an American film actor most famous for gangster roles in the 1930s and 40s, as well as for his alleged Catch Phrase. He starred in some of the best gangster pictures ever made, including Angels with Dirty Faces, White Heat, The Roaring Twenties, and The Public Enemy, which is unfortunately mostly remembered for a scene in which he shoves half of a grapefruit into a woman's face.

The Other Wiki has more to say here.