‘City’ Life’s Good for Thompson : Television: With a big boost from a killer time slot, her show is putting up big numbers in the ratings wars. Not bad for a newcomer to sitcoms.

Actress Lea Thompson was not having a particularly great day. Her 4 1/2-year-old daughter, Madeline, had fallen ill recently and, as a result, the star of NBC’s new comedy series “Caroline in the City” had only managed to get a few hours of sleep the previous night.

To compound matters, this had been a longer-than-expected rehearsal day and now Thompson was experiencing major problems locating her car and house keys.

It’s tough being a working mother.

“It’s tough being a mother, period,” Thompson corrects with a knowing smile.

Nevertheless, as she settles in for a post-rehearsal interview on her show’s Studio City set, Thompson is amply aware that life could be far worse for one of TV’s newest sweethearts.

Thanks in no small part to a to-kill-for time slot on Thursday nights between the beloved “Seinfeld” and the mega-popular “ER,” “Caroline in the City” is putting up big numbers in the dog-eat-dog television ratings wars. The sitcom--which finds Thompson playing an unmarried cartoonist living in New York City--is this season’s fourth-highest rated series. “Caroline” also chalked up the best November sweeps numbers for a new show since “A Different World” in 1987.

The show’s success has been particularly gratifying for Thompson since, unlike many television comedy stars, she entered the project with zero experience as a sitcom actor or as a stand-up comedian. Since debuting in the cheesy feature film “Jaws 3-D” in 1983, the 34-year-old Minnesota native has worked primarily as a character actress in numerous feature films, TV movies and stage plays. She is perhaps best known for her role as Michael J. Fox’s mother/girlfriend in the three “Back to the Future” films.

“I understand why it’s good to come from stand-up comedy because then you have an act and the writers [can use that as a source] for laughs,” she observes. “It was not that easy for me. Also, because Caroline is the girl-next-door, there are some constraints put on that character. That’s why people have had trouble doing ‘The Mary Tyler Moore Show’ again, because she was a nice girl in a funny world. That’s a hard thing to do.”

“Caroline in the City” is Thompson’s show, yet she only occasionally gets the funniest lines. When it comes to eliciting the big laughs, it’s not unusual for her to defer to her more colorfully cast cohorts, who include Malcolm Gets as her cantankerous colorist, Richard; Amy Pietz as her man-craving best friend, Annie; and Eric Lutes as her on-again-off-again boyfriend, Del.

While she believes the show attempts to push the envelope of what is acceptable in a girl-next-door type, Thompson realizes that her primarily role is to be the show’s anchor and lovable protagonist. She feels her steady presence allows the other characters the room to be outrageous.

It was NBC Entertainment President Warren Littlefield who pushed for Thompson to star in her own TV series for the network. He had been particularly impressed with her performance in the 1994 NBC movie “The Substitute Wife.”

The idea of both steady work and steady hours appealed to the actress, who was then pregnant with her second daughter, Zoey, now 1. Thompson says her current work schedule often enables her to take Madeline to school in the morning and to get home in time to prepare dinner at night. (She’s married to filmmaker Howard Deutch, who directed her in the 1987 film “Some Kind of Wonderful.”)

Thompson conveys a warmth and sweetness that does not appear at all disingenuous. Though she has an effervescent side, she describes herself as a naturally shy and reserved person. Thompson also says she’s managed to pick up some of Caroline’s humor and aggressiveness.

“I’ve gotten funnier at dinner parties since I’ve been doing this show!” she says with a laugh. “I think it’s because people kind of expect you to be funny. But I’ve also gotten more outgoing. Being the center of the show, you have more of a responsibility than the other actors about showing up, behaving and being conscious of things on the set and the characters. You have [to be willing to] talk to the writers. It’s been a growing-up [process] to take that kind of responsibility.”

Not everyone has fallen in love with “Caroline in the City.” Despite its impressive ratings, the sitcom has generated yawns from more than a few critics. Some have questioned how well the show would do outside of its choice time slot.

Still, “Caroline” has fared far better than the failed sitcom “Madman of the People,” which occupied the same time position last season. Thompson says NBC has not interfered at all with the making of the show and that there are no major changes in the works. The producers are planning to bring in a new love interest for Caroline toward the end of the season. But Thompson insists that old boyfriend Del isn’t being phased out of the picture.

“The network has been wonderful with this show,” she states. “They have not come in here and messed with us. I’d always heard, ‘They’re going to do this and they’re going to do that.’ That was always the party line on the network. But we never see the bigwigs. It’s like, ‘You guys are doing great. Go ahead and play!’ It’s been a wonderful experience for me.”

Thompson has an appealing way of not taking anything for granted. Having grown up poor, there are still times when she can’t believe she’s not living hand-to-mouth. She says the Thompson family still has a love for thrift stores and garage sales. “It’s a real strange bonding thing with my family,” she explains. “It’s about recycling and treasure-hunting.”

Thompson credits her multi-talented mother for her interest in the arts. Now in her mid-60s, she is described as a painter, musician, songwriter, sculptor, director and actress.

“She always made me feel that it was OK to be an artist and that it was even cool to be poor,” recalls Thompson, the youngest of five children who was also raised by an insurance executive father and a printer stepfather. “I didn’t have a bad opinion of myself because of that.”

Thompson’s first love was actually ballet. At 17, she began a 2 1/2-year apprenticeship with the Pennsylvania Ballet Company. This was followed by a brief stint with the farm company of the American Ballet Theatre. But she gave up the craft at the age of 21 when she realized that she didn’t have a strong enough body to be a ballerina.

She immediately made the successful segue to acting.

“I love to act,” Thompson says. “I love the different challenges that I get every week [with “Caroline in the City”]. It’s been a real gift.”

* “Caroline in the City” airs Thursdays at 9:30 p.m. on NBC (Channel 4).