The character Sully Sullivan (James Woods) is loosely based on Boston's infamous gangster, James "Whitey" Bulger. In the series, Mickey Donovan was a consultant in a film called "Black Mass", the same name of Bulger's real-life biopic starring Johnny Depp.
Ted Levine is playing the owner of Buffalo Bill's casino. A great homage to his character of the same name from The Silence of the Lambs (1991).
When the show got canceled after season 7, there was such an outcry from fans that the producers and the network figured out a way to wrap up the story with a TV-Movie.
The necklace Ray Donovan wears carries a Saint Genesius medallion pendant. Saint Genesius is considered the patron saint of actors, lawyers, barristers, clowns, comedians, converts, dancers, people with epilepsy, musicians, printers, stenographers, and victims of torture.
The first five seasons are set in sunny, warm Los Angeles and those seasons premiere in the warm summer months. Season 6 & 7 taken place on the east coast and premiere in the colder fall months. The main reason for the change was that after Liev Schreiber's breakup with Naomi Watts, he wanted to be in New York, where he lives, to be with his children daily.