So we all know Jack Nicholson's original infamous line goes like this: Woman: "How do you write women so well?" Melvin: "I think of a man, and I take away reason and accountability." The line is funny. Of course it's not true, but it does invite this question: Have you ever created a character by thinking of someone (famous perhaps) and changing his or her gender? What would you take away? What would you add?
Recently, I've come to think along a different vein... I think of myself in a situation where I reacted emotionally in a way that fits for a character. For instance, in 1994, having spent the previous ten years of my life preparing to spend the rest of my professional years as a programmer of the most advanced computer platform of the day, the rug was pulled out from under me when the company went out of business. Feeling betrayed, angry, resentful, and well past my prime, I was faced with starting over again from scratch with an inferior platform and realized I simply couldn't find the wherewithal to do so. I ended up going in a completely different direction which has yet to bear fruit. Applying that to the focal character in my WIP, I find myself understanding his every nuance and motivation even though his circumstances are vastly different from mine. Instead of starting with a someone and changing/taking away/adding, I start with myself and apply it as an emotional overlay, so to speak.
I cannot say that I have ever considered this before. Instead I try to focus on making them simply people you would ordinarily find in every day. And some a bit less so, but certainly not any of fame. By using little bits of real people (that I know or have known) and smushing them into a single persona, or I build them from the foundation up from scratch.
There's a somewhat similar and interesting thread back here. To reiterate my post from it, I don't really take gender into account when I design characters, so changing their gender wouldn't make much difference.
I've actually tried to come up with characters who are based on other people, and it doesn't work With only one exception that I can think of, I need to come up with my characters completely from scratch, or they don't feel real to me. One exception, that's it. Of all of the dozens of characters I've come up with, I can only think of one exception to this: When I started my Doctor Who fanfiction, I decided that since two of the characters in the official series were made to be superficially similar (omnisexual former Time Agent who goes by the alias of Captain Jack Harkness, omnisexual former Time Agent who goes by the alias of Captain John Hart), therefore I would come up with a character for my own story who would follow the same theme (omnisexual former Time Agent who goes by the alias of Captain June Harper). The best part is that the superficial similarities between the two official characters were supposed to make the fundamental differences stand out more strongly (Jack Harkness was a heroic leader, John Hart was a villainous loner), so it was really easy to do the same thing with my own character: June Harper was originally supposed to be a heroic leader, that was already a distinction from John Hart, so my next step was to make her a different kind of heroic leader than Jack Harkness (and rewriting her as a serial killer only made this even better because now she's a villainous leader) Jack Harkness is very casual with the people on his team – when there's no apocalypse in the making, he has no problem joining the office basketball games – but the only one that he's close to in any way is that guy that he's completely In Love With; everybody else is just a person to be around, not a person to connect with. June Harper, on the other hand, is not in love with anybody on her team, but she is a lot closer to all of them on a friendship level than Jack Harkness is with his employees. Sure, technically I made my female character a lot more emotionally available than either of the two male characters, but with the number of male characters in my work who are extremely touchy-feely and the number of female characters in my work who are not, I'm not sure that this example reflects on any general principle beyond just a Law of Large Numbers coincidence.
I rip off people's mannerisms and foibles all the time. This got me into some major shit with my wife once...
Nicholson was portraying a romance writer though. Women in that genre can get away with being unbelievably irrational as it's an emotion led genre. It's difficult to criticize Bella Swan and Ana Steele because they're major success stories. Whereas when Anita Blake started to act like that her story jumped the shark, because her genre doesn't allow for that sort of anti reason.