A veteran of stage, television and movies, actress Susan Sullivan was born November 18, 1942 in New York City. She is perhaps best known for her role as Maggie Gioberti on Falcon Crest and as Greg's mother Kitty on Dharma and Greg.
Initially, she didn't think she was right for the part of Martha and suspects she got the part when, in the audition, she had to read with Nathan Fillion, and she stood up from a chair, while he stayed seated. She remained in character, telling him to get up, giving the crew as well as herself and Nathan, a good laugh. "I think it was that quality more than anything else, which is part of the dynamic of their relationship," she said.
Susan has said that her performance is partly an homage to her own mother. One of her favorite scenes on the show came during Little Girl Lost in which the writers included one of her mother's own quotes: "[My mother] would say all the time, 'You is who you is. If you ain’t who you is, who is you?' When Martha was being a life coach in the first season she would have clients come over and she’d be telling them in her own way how to live your life, which of course is what she does with Castle and with her granddaughter. She’s great at telling people how to live. My mother would do that on a park bench — God forbid you sat down next to her!" Another of her favorite scenes took place in Knockdown when Martha severely admonishes Castle for asking her why she is so concerned about his safety while working at the precinct. "I like that moment because it was grounded in the truth of her deep love for her son."
She has said the part of Martha "a fantasy part" and that "she mirrors many of my own fears [including] aging and how you try to hold on to being still in the game." She has gone on to say that she relates to her character to a certain extent: "The character as originally written, I think, was a little bawdier...And a lot of her issues — you know, feeling a little marginalized, wanting to stay in the game, wanting to be active, wanting to have something to do, wanting to have this connection with her son and her granddaughter — all of those elements I can certainly identify with, and I think most women can." 
Regarding her relationship with Nathan Fillion, says "I absolutely adore him...I know everybody always talks a big game about how great everything is and sometimes it’s true and sometimes it’s not, but in this case I can tell you it really is true. It’s a delight. He’s a very intuitive and sensitive man." She's also called working on the set of the show "an extended family of my own."
Her Castle co-star Molly C. Quinn had the following to say about Susan: "Susan is so sophisticated and elegant. Just the way she carries herself with so much grace and dignity. It’s a huge example to me. Plus, she’s fun. I mean, she doesn’t go around giving advice like some people do, but If I ask her she’s really open and talks from the heart. So it’s nice to have her around. I really love her — she’s great."
Selected Television Roles
- The Nine - Nancy Hale, 7 episodes
- Brothers and Sisters - Miranda Jones, 1 epsiode
- Two and a Half Men - Dorothy, 1 episode
- Hope and Faith - Dr. Nancy Lombard, 7 episodes
- Justice League - Queen Hippolyta, 7 episodes
- Judging Amy - Patricia Millhouse, 2 episodes
- The Drew Carey Show - Annette Newmark, 3 episodes
- Dharma and Greg - Kitty Montgomery, all episodes
- The Monroes - Kathryn Monroe, 8 episodes
- The George Carlin Show - Kathleen Rachowski, 6 episodes
- Falcon Crest - Maggie Gioberti/Maggie Channing, 207 episodes
- Fantasy Island - Dorothy Nicholson, 1 episode
- Taxi - Nora Chandliss, 1 episode
- The Love Boat - Dr. Emily Bradford, 1 episode
- Barnaby Jones - Linda Gates (2 episodes) and Ruth Sorrel (1 episode)
- The Incredible Hulk - 1 episode
- Rich Man, Poor Man (Book 2) - Maggie Porter, 20 episodes
- Kojak - Kelly McCall (1 episode) and Carol Krug (1 episode)
- McMillan & Wife - Maggie Arnaud, 1 episode
- Medical Center - Joanna Courtney, 1 episode
- Ironside - Andrea, 1 episode
- Another World - Lenore Moore Curtin Delany
- My Best Friend's Wedding - Isabelle Wallace
- Perry Mason: The Case of the Ruthless Reporter (TV movies) - Twyla Cooper
- The Incredible Hulk (TV movie) - Dr. Elaina Marks
Selected Theatrical Roles
- Jimmy Shine opposite Dustin Hoffman
- The Fifth of July
- Last Summer
- Attended Hofstra University
- Was a Playboy Bunny in the 1960s while in college and often recited Shakespeare while waiting on customers
- Is 5' 7 1/2" tall
- In Castle episode Tick, Tick, Tick. – (Part 1), Martha is seen watching a recording of Susan's real appearance in the TV show The Incredilbe Hulk.
- Has been a long-time spokesperson for the pain reliever Tylenol.
- When asked which member of the Castle cast is most like their character, her co-star Molly C. Quinn said that Susan is classier than Martha.
- Has a reputation, leftover from her stint on Falcon Crest, for being a practical joker
- Has become a fan of American Idol since Jennifer Lopez became a judge.
- Wears a wig when portraying Martha, as she is a natural blonde.
- Her favorite Castle episode is He’s Dead, She’s Dead when Martha had to deal with the death of her boyfriend Chet and her favorite project in her career has been her role on Dharma and Greg since it was her first comedic role on a television show.
- "One-on-One with...Castle's Susan Sullivan" interview by Jim Halterman, posted March 21, 2010
- Wetpaint Exclusive: Castle Mom Susan Sullivan teases Season Finale's "Love and Loss", Weptaint.com, written by Ian Spiegelman, posted April 6, 2011
- "What's Next for Castle's Crew", page 19, TV Guide, Feb. 28-March 6, 2011
- " Castle Star Molly Quinn Calls the Season Finale "Phenomenal" and "Crazy" Wetpaint.com, written by Ian Spiegelman, posted April 14, 2011
- Susan Sullivan biography at the Internet Movie Database
- An Evening with Castle at The Paley Center for Media, March 16, 2010
- " Castle Star Susan Sullivan Dishes About Martha's Wardrobe, Dream Guest Stars and On-Set Pranks", Wetpaint.com, written by Ian Spiegelman, posted April 11, 2011