This is a reference to James Cagney (1899-1986), the American film actor. One of the most iconic actors of his time, he was mostly known for playing 'tough guys'.
He won an Oscar in 1942 for his role in Yankee Doodle Dandy. In 1961, he retired for 20 years after suffering a stroke. He had a difficult working relationship with Warner, walking out several times and eventually suing the studio for breach of contract. His victory set a new precedent for actors. He made a series of morale-boosting visits to troops fighting in the Second World War, and served as President of the Screen Actors Guild for two years.