Mary McCormack has always wanted to play a character like Mary Shannon.

"It's a great tomboy role, and I've been looking for it forever and ever and ever," said McCormack, who's starring as a U.S. marshal working in the highly secretive branch of the witness protection program in the new USA network series "In Plain Sight," which premieres Sunday at 11 p.m.

"I'm thrilled with that, and I can't wait to beat a bunch of people up."

Mary Shannon is a tough woman who does indeed beat a few guys up, but she's also smart, funny and her personal life is "a train wreck." And McCormack can relate. She said she "found a lot of similarities" between the character and herself.

"It's sort of spooky, actually," she said. "I mean, sadly, my personal life isn't always so together, and I think anyone can relate to that, especially people who work a lot and work hard. Sometimes your personal life is the last thing you take care of.

"She calls her sister 'Squish,' and I call my daughter 'Squish.' She's from New Jersey. I'm from New Jersey. There was a bunch of little sort of quirky similarities that really struck me."

And that may partially explain why McCormack is so great in the part.

"There's an acerbic element as well," said Fred Weller, who co-stars as her partner, Marshal Marshall Mann. (Yes, his first name is Marshall.)

"Are you calling me acerbic?" McCormack interjected.

"Maybe," Weller replied. "Difficult to get along with."

He was kidding about McCormack (I think), but Mary Shannon is tough and a bit difficult to get along with. You can hardly blame her, however, because she's got a nearly impossible job she can't really talk to her family about.

Her mother (Lesley Ann Warren) is pretty much impossible; her sister (Nichole Hiltz) is worse — and she's got a secret; and Mary hardly has time for her boyfriend (Cristan de la Fuente).

Her job is to keep people alive when other people are trying to kill them. Some of her charges are criminals; some of them are just unfortunate individuals who happened to be witnesses; all of them have been yanked out of their regular lives and dropped in her lap.

David Maples, the creator/writer/executive producer of "In Plain Sight," said he was also struck by the similarities between Mary McCormack and Mary Shannon but insisted that they were all coincidental.

"(Mary Shannon) is an amalgam of a couple of different women that I've known in my life who were just kind of fun, challenging, not always appropriate, kind of crusty on the outside, but once you kind of get past all that and they let you into their world, it's incredibly rewarding," Maples said.