Shirley MacLaine Wishes She Hadn't Turned Down Iconic Audrey Hepburn Role: 'Couldn't Stand the Idea' (Exclusive)

Certain roles are inseparable from the actors who portrayed them.

Who can imagine, for instance, anyone but Meryl Streep as the title character in The Devil Wears Prada? And would Sex and the City's Carrie Bradshaw have been Sex and the City's Carrie Bradshaw with any actress other than Emmy winner Sarah Jessica Parker playing her?

And then there is Holly Golightly, the iconic character that the iconic actress Audrey Hepburn played to perfection in the 1961 classic Breakfast at Tiffany's. What if she had been portrayed by, say, Shirley MacLaine, who at the time was a rising star fresh off an Oscar nomination for her performance in the 1960 film The Apartment?

It could have happened, MacLaine, 90, reveals in her new book The Wall of Life: Pictures and Stories from This Marvelous Lifetime. The Holly Golightly role was initially offered to her, she says; of course, she turned it down. The rest is cinematic history.

"I didn't want to have to worry about my weight to be able to wear all those outfits and do all those fittings," she writes in the book, adding that she also "didn't think it was a very good script."

Although she writes that she "doesn't really regret" her decision, in hindsight, she tells PEOPLE, it's the one film she didn't do that she wishes she had done. Too bad about those pesky fittings!

"Well, listen, I'm a well-known disliker of fittings," she explains in an exclusive interview. "I don't like fittings, and I knew that would take a lot of fittings." Also, she adds, "I wasn't sure about the script because it was so much about how I would look, therefore, about how many fittings. That's really it. I couldn't stand the idea."

"I wish I'd had the patience for those wardrobe fittings."

So what did she think of the movie? "I never saw it," she says. "I haven't seen it. I don't know because I still think it's about wardrobe."

Hepburn would go on to score an Oscar nomination for Breakfast at Tiffany's. And ironically enough, she and MacLaine would costar in MacLaine's follow-up to The Apartment and Hepburn's very next film, 1961's The Children's Hour. In the book, MacLaine says she "adored" working with Hepburn.

"She taught me a little about dressing; I taught her a little about cussing," she writes, adding that they remained friends for years.

At the time of its release, The Children's Hour, based on Lillian Hellman's lesbian-themed 1934 play, was a risky move for two big stars.

"No question about it," MacLaine says. "But Audrey and I both grew up in the ballet world, so we had no problems with how to accept that. She was a dancer, too. Not as professional as I was, she gave it up earlier, I think. But of course, we grew up in a gay world, and so we just wanted to do our part in championing it."

The Wall of Life will be published on Oct. 22 by Crown Publishing and is now available for preorder, wherever books are sold.