HOLLYWOOD - In the tradition of Joan Blondell, Billie Burke and Carole Lombard, Katherine Heigl is a gorgeous blonde who loves making movie audiences laugh. Her favorite genre is the romantic comedy. She likes watching them almost as much as she likes making them.

Though she is best known for playing Dr. Isobel "Izzie" Stevens on the ABC medical drama "Grey's Anatomy," Heigl has carved out a niche for herself on the big screen over the past few years in romantic comedies.

Her calling began with 2007's "Knocked Up," the Judd Apatow-directed comedy in which she played a TV entertainment reporter who is impregnated by a ne'er-do-well slob (played by Seth Rogen) after a night of drunken misadventure. Heigl wowed audiences with her comedy chops and willingness to "go there" with Apatow's crude humor.

She later co-starred opposite Ed Burns in the more traditional rom-com "27 Dresses," playing a serial bridesmaid who finds herself in love with her sister's fiancé.

Last year, she co-starred with "300's" Gerard Butler in the rom-com "The Ugly Truth," in which she played a romantically challenged TV producer who reluctantly enlists a chauvinistic colleague to give her dating advice, only to discover a sexual chemistry with him.

The Washington, D.C., native now co-stars with Ashton Kutcher in "Killers," playing a suburban housewife/computer tech who discovers her seemingly ordinary husband, an architect, has a secret past profession that could put them both in danger. The film opens today.

"What I love about this particular romantic comedy is that it has the added element of action," said Heigl. "It's a slightly different take on the formula."

Written by Bob DeRosa and T.M. Griffin, "Killers" reunites Heigl with her "Ugly Truth" director Robert Luketic. It was shot last year in Nice, France, and various locations in and around Atlanta.

"Killers" afforded Heigl an opportunity to show off her nerdy side. Her character Jen, a computer geek, is completely clueless about her husband Spencer's past and doesn't know how to deal with the sudden onslaught of violence around her. She screams and squeals a lot and doesn't know how to handle a gun.

"I loved being the broad character to Ashton's straight guy," she said. "It was really fun to not be the straight guy for a change.

Kutcher serves as a producer on the comedy as well as Heigl's co-star. He had been looking for a buddy-cop comedy to star in before getting the "Killers" script but warmed to the idea of a female partner when he read the script.

Married to singer-songwriter Josh Kelley for just under three years, Heigl could identify with the adjustments facing a new bride. "My husband is better at most everything than I am," she said. "What I love about this particular film is that Jen is kind of dorky . . . and that's what Spencer loves about her."

She said accepting your partner's silly or funny quirks are what make for a happy marriage.

The couple recently adopted a baby girl from South Korea, and Heigl is having the time of her life as a first-time mom. They named her Nancy Leigh, after Heigl's mother and sister, respectively.

Heigl's priorities have changed in other ways. "I hang out with my friends and my husband a lot," she said. "I watch my daughter toddle around. I spend a lot of time at home just chillin'. It's my favorite thing to do right now."

While her "Killers" character is blindsided by her husband's revelation, Heigl takes a different stance on marital secrets. She said it's OK for spouses to keep secrets, as long as they don't emotionally hurt or physically endanger the other.

"I, unfortunately, have a very difficult time keeping secrets, which is evident in any interview I've done," she said. "I don't think my husband has any, but if he did, I think it's OK, because everyone has a right to their own thoughts. I mean, if he had a secret wife in Spain that would be a big secret to keep, but if he's using Rogaine, that's OK. He doesn't have to tell me."

Heigl, 31, started out as a model but took an interest in acting at a young age. She made her professional acting debut while still in high school in the 1992 romantic drama "That Night," and had her first starring role two years later in "My Father The Hero."

She left her Connecticut high school for Hollywood before graduation, and she soon found herself starring on the sci-fi series "Roswell."

In 2005, Heigl landed the plum role on "Grey's Anatomy," playing a medical intern who wants to be taken seriously by her colleagues. She earned an Emmy award in 2007, but her relationship with the show's producers began to sour when she publicly criticized the development of her character during the fourth season. Her character gracefully exited the show earlier this year after a near-fatal illness and a romantic breakup. (The show is slated to return for its seventh season this fall without Heigl.)

Heigl's comedic influences include Shirley MacLaine as well as Catherine O'Hara, who plays her mother in "Killers." ("Magnum, P.I.'s" Tom Selleck plays her father.)

With "Grey's Anatomy" behind her, Heigl is poised to focus on her movie career.

She is set to star opposite Josh Duhamel this fall in the drama "Life as We Know It," directed by Greg Berlanti. She will serve as an executive producer through her production company Abishag, which she runs with her mother.

She soon will start production on "One For the Money," which she also is executive-producing. She stars in the film as brunette bounty hunter Stephanie Plum (which explains her new hair color). The story is based on the first novel in the best-selling series by Janet Evanovich.

"I'm so excited about it," said the actress. "I didn't really know much about the books until I got [the script], so then I started reading them and then I got obsessed with them."

Having read all 15 books in the series, she now feels vested in them.

"I'm afraid I'm not going to live up to my own expectations," she frets. "But it's a really fun challenge and it's really exciting."