She had an inkling that's what it would take for her strong, flawed character on Grey's Anatomy, Dr. Addison Montgomery-Shepherd, to click with the show's audience.

Her role as the estranged spouse of Derek Shepherd (Patrick Dempsey), although initially intended to be short-term, took shape the longer she was on screen.

Initially Addison, a neo-natal surgeon, was hated by fans who saw her as standing between Meredith and McDreamy and true happiness.

But as Addison's story lines evolved, she became one of Grey's Anatomy's most beloved characters.

Not a bad effort.

"They started off writing her like the wicked witch from the east all in black coming in to clean up. And then they just gradually made her more and more human and took off the scales one by one," Kate Walsh said.

"They do this with everybody in the show. All the characters have a work persona and a personal persona. I think that's just very real, and that it is also very natural that some people would reveal theirs more than others, like the interns that are working 400 hours a week."

The public reaction to Addison has changed from anger over McDreamy to joy at seeing her in the arms of Dr. Mark "McSteamy" Sloan (Eric Dane). The character is so popular, producers gave her a spin-off series.

Walsh left at the end of Season 3 to begin Private Practice, which viewers have already had a taste of in a previous episode of Grey's Anatomy.

The series is set in L.A. and also stars Taye Diggs and Tim Daly.

"Basically, where Grey's Anatomy is sort of people who worked together that become friends, these are all friends already, and they got together and decided to form a private practice," Kate Walsh says.

The newly-engaged actress adds that viewers can expect to see more of the characters' "messy personal lives."

Also waving goodbye to Grey's Anatomy is Isaiah Washington, who played Dr. Preston Burke. Washington and Shonda Rhimes (executive producer of both Grey's and Practice) have been surrounded by controversy since his departure.

One character definitely back for season four is Justin Chambers' Alex Karev. While seeming arrogant at first, Alex's layers have slowly been peeled back to reveal a more caring side.

"He definitely has been humbled," Chambers says. "He's had a big piece of humble pie. Who knows if he'll go back to being a jerk."

Justin Chambers says he discovered, through his own research, that many surgeons are actually quite arrogant.

"Some of them do have a bit of a God complex, in large part because people's lives are in their hands," he says. "But what makes this show work is that we see these doctors in a professional mode, but then we see that they are human and they are flawed, and every character on the show has issues... and I'm sure plenty of surgeons in real life are similarly flawed."

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.