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).
Calabasas, where Ray Donovan and his family make their fictional home, is a California community, where many A-list celebrities such as Will Smith, Cameron Diaz, Jennifer Lopez, Britney Spears, the Kardashians, Kanye West, Tori Spelling, Richie Sambora and Nikki Sixx make their real-life home.
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.
In the show, Terry is oldest brother. In actuality, Liev Schreiber is eight months older than Eddie Marsan.
Ian McShane and Paula Malcomson appeared on Deadwood (2004). Austin Nichols (Tommy Wheeler) also appeared on Deadwood in 2 episodes as Morgan Earp.
Liev Schreiber and Susan Sarandon (who joined the show for season five in 2017) appeared in Twilight (1998).
The second season featured Brent Spiner as Ray's psychiatrist and Wendell Pierce as Mickey's parole officer.
Domenick Lombardozzi, Tony Curran, Pasha Lychnikoff and, Eddie Marsan all featured in the 2006 Miami Vice movie.
Hank Azaria (Ed) and Jon Voight (Mickey) were both in Uprising (2001), a 2001 TV movie documenting the Warsaw Ghetto uprising.
The third season has Aaron Staton as Bridget's teacher, Ian McShane as Malcolm Finney, and Bronson Pinchot as a television talk show host.
Liev Schreiber and Dash Mihok have appeared in modernized versions of William Shakespeare's plays: Mihok appeared as Benvolio in William Shakespeare's Romeo & Juliet (1996), and Schreiber appeared as Laertes in Hamlet (2000).
Liev Schreiber and Paula Malcomson play husband and wife in this show, however they both would appear in "crime scene investigation" (2000-15). Even though they don't appear in the same episode or even the same season but Liev would appear in several episodes in season 7 and Paula would appear in season 9 episode 12 of "CSI".