Physicists and philosophers be damned -- Nicole Sullivan can, in fact, be in two places at one time.

She is currently starring in both Mad TV, the Fox sketch comedy taped in L.A., and Talk to Me, the ABC sitcom filmed in New York.

"With a sketch show, you can bank sketches. I can shoot a bunch and they can put them in different shows," Sullivan says.

Talk to Me will return to ABC's schedule after the May sweeps period. It's true, however, Sullivan is finishing with Mad TV after five seasons to concentrate on primetime projects.

"My original contract was for five years and I think they let me out a little bit early. The production company and Fox were really great about this," she says.

While Talk to Me kept Sullivan busy this winter, she does admit to already missing Mad TV.

"There's already been a withdrawal for me," Sullivan tells the Sun.

"It was sort of like a baby to me. I was there from the beginning, part of the original troupe."

Launched as a direct competitor to Saturday Night Live, the series created by Quincy Jones and David Salzman (Jenny Jones) was not given much of a chance for survival.

Indeed, Mad TV struggled for the first few seasons but benefitted from a half-hour jump on SNL's U.S. timeslot and a faster pace than its sagging NBC counterpart.

"Can we make something out of this Saturday night slot?" Sullivan remembers wondering during the early days.

"We did it, and it makes me more proud than probably anything else in my life. That's an incredible feeling."

The series, which airs Saturdays at midnight on c, recently celebrated its 100th episode.

This weekend's guests are Susan Sarandon, Dennis Hopper, and Garry Marshall.

Catherine O'Hara and George Carlin appear next week.

The Mad TV cast has included Artie Lange, Phil LaMarr, Will Sasso and Alex Borstein.

"The thing I'm going to miss the most is that creative outlet. We sit there talking over lunch doing a bit and two weeks later were recording that bit," Sullivan says.

"Anything you can dream up, you can do ... theoretically. They still say no sometimes."

Sullivan is best known for her snooty character, the Vancome Lady. Her regular characters also included fast-food employee Antonia, news anchor Diane Lawyer-Trabajo and one half of the duo Molina and Lida.

Now with Talk to Me, Sullivan is limited to one role: Kat, the shiftless sister of radio DJ Janey Munro (Kyra Sedgwick).

It's the sort of situation Sullivan used to spoof on Mad TV with Felicity, Three's Company and Dharma & Greg parodies.

"I like the idea of getting to do one character really well," Sullivan says. "In a sketch, you just have to make them funny. And on a sitcom, you have to make a character funny and real."

With Janey trying to put her life together after a break-up, it's nice to have Kat around. Her life always seems to be in pieces.

"She's someone who really never has a job. She prefers to volunteer and it probably doesn't occur to her she can't pay rent that way," Sullivan says.

Luckily, her successful sister is there to help Kat and bail her out when she gets into the zany mix-ups sitcom characters tend to find themselves in.

"Kat's such an optimist, such a believer that everyone's good at heart," says Sullivan.

"It's good balance to Kyra's jaded and sarcastic character. They make a really nice combo."

ABC hasn't made a decision on the mid-season series yet, but it seems hard to imagine Sullivan being out of work long if Talk to Me doesn't make the fall schedule.

Other '90s sketch comedies have already launched sitcom leads David Spade, Jamie Foxx, Andy Dick, Jay Mohr, Norm Macdonald and Dave Foley.

The Edge, a short-lived Fox effort, alone featured Jennifer Aniston, Wayne Knight and Alan Ruck.

Yet Sullivan denies she left Mad TV in the hopes of getting her own series.

"If I want to act for 30 years, I'll eventually do other things -- hopefully," she says.

Perhaps Sullivan is looking even beyond to following Jim Carrey, Ben Stiller and Mike Myers directly to the big screen?

"I don't look at television as a stepping stone to film or anything like that," Sullivan insists.

"Of course, dear God, I'd take a (movie) job. I'd sell my right arm and everything I own.

"But as a way of life, I like the way TV works. I want to stay on television for a while.

"This may change next week, though."