So it was hardly a dream of the actress -- best known as Capt. Kathryn Janeway on "Star Trek: Voyager" -- to portray the legendary Hepburn in aone-woman show.
But playwright Matthew Lombardo had no idea how Mulgrew felt about Hepburn. They hadn't met. While watching an episode of "Voyager" with friend Nancy Addison, Lombardo exclaimed, "That actress should play Katharine Hepburn."
Addison, who appeared for years with Mulgrew on "Ryan's Hope," replied, "That actress is my best friend. If you write something I'll make sure she reads it."
It took Lombardo just three days to complete a draft of "Tea at Five."
"I remember when I received it thinking, 'This is going to be great or a disaster,' " Mulgrew said. She quickly decided it was the former.
"Tea at Five" premiered in 2002 at Connecticut's Hartford Stage and has graced several venues since then, including a successful off-Broadway run at the Promenade Theatre in New York City. Beginning Friday it's at the Pasadena Playhouse for a run through Oct. 2.
"Maybe it was because I was so often compared to her that I naturally found her not my cup of tea," Mulgrew explained. "But all of that was expelled during the rehearsal process. I learned that she truly wanted to be more than a movie star. She wanted to be a great actress."
That she was. Hepburn, who died at age 96 in 2003, was perhaps the most decorated performer, male or female, in the industry. Over her seven decades in show business, she won more Oscars for lead roles -- four -- than anyone.
Portraying an icon was no doubt a bit daunting. But Mulgrew, at least, got to have a say in the script because the play was written specifically for her. A stickler for detail, she insisted that Lombardo show at least three sources for any quotes she found sensitive, particularly ones regarding Hepburn's relationship with married actor Spencer Tracy.
The play consists of two conversations between Hepburn and the audience. The first takes place in 1938. Hepburn, 31 years old, has suffered through a string of poorly received movies and is anxious to revive her career. In the second act, Hepburn is 76, and more contemplative and relaxed.
To prepare, Mulgrew watched every movie and read every book or article she could find.
"It was good that we opened in Connecticut so I could shut myself in my room every night without distractions," she said. "I came out with a robust body of knowledge about her that I then had to throw away on opening night and hope that it all worked. And it did."
For Mulgrew the moments in the play that resonate most strongly are when Hepburn talks about her brother's suicide as a teenager and about her relationship with Tracy.
"It's surprising that she put up with him, that she accepted it all," she said. "He was married and a boozer and a womanizer."
Mulgrew, who never met the legend she portrays, believes audiences continue to be drawn to "Tea at Five" because Hepburn's presence was so alluring.
"We don't want to let this woman go," she said. "We're so proud of her. She had grit. Nobody walked like her. Nobody talked like her. She broke down the door to the boy's club when that was unheard of. She was private, smart and intellectually curious. She was filled with confidence, whether fabricated or not."