It took about three years after going off the air for Fran Drescher to stop rewriting the jokes in her head.

Every time she would catch a rerun of “The Nanny” on TV, she’d think of a better set up — a quicker punchline.

“Now, I can be peaceful,” she says. “I can enjoy it for what it was.”

What it was was six years of “The Odd Couple” –Fran Fine as Oscar and Mr. Sheffield as Felix — with a biological clock thrown in.

More important, “The Nanny” was a New York show in a way that, say, “Friends” or even “Seinfeld” (which were on the air in the same years) were not.

Face it, “Seinfeld”– despite all the Jewish jokes — could have been set in Boston or Chicago, no sweat.

Fran Fine could not have come from anywhere else in the solar system but Queens.

The show’s basic theme — that the upper classes could learn plenty from working folks — wasn’t the kind of thing that Rachel, Ross and Phoebe worried about.

Nick at Night is running a week-long Valentine’s marathon of “The Nanny” that starts tonight (11 and 11:30 p.m.). Drecher handpicked the 14 episodes and taped new intros.

The actress stresses over how skinny she used to be (“It’s amazing how thin you can be if you stop eating”) and admits there are episodes where “I didn’t love my hair.”

Nowadays, she points to season five as the moment the series hit its peak.

Big stars like Elizabeth Taylor (whose reps instructed the cast that “she likes to be called ‘Elizabeth’ not Liz”) and Elton John (who required a large bouquet of red roses in his dressing room every day) were clamoring to guest on the show.

But quickly, it all came undone.

By season six in 1999, CBS told her the ratings were “getting softer and that, if we wanted to wrap up the story, we should get ready,” Drescher says.

In hindsight, it may have been a blessing the show was cancelled.

During that final season, her 21-year marriage to Peter Marc Jacobson, the show’s chief writer and co-creator, unraveled just as she had begun to feel sick.

After several missed diagnoses, Drescher was told not long after filming ended that she had a slow-growing uterine cancer. A week after that, she underwent a hysterectomy.

“I learned the hard way,” she said last week. “You don’t know what’s going to happen five minutes from now.”