As the first of tonight’s new series proves, creating TV programs isn’t rocket science.

You just take elements of other popular shows and mash them together. If you do it well enough, the viewing public just might buy it as something original.

For example, take the science from “C.S.I.” and the military trappings of “JAG,” blend them well, and you’ve got “Navy NCIS,” debuting at 8 tonight on CBS.

NCIS stands for Naval Criminal Investigative Service. They are in essence the cops who are the flip side of the lawyers from “JAG” (also produced by Donald Belissario).

Leading the unit is Special Agent Leroy Jethro Gibbs (Mark Harmon, “Chicago Hope”), a skilled investigator who will bend the rules to get things done. He’s aided by a former homicide detective (played by Michael Weatherly, “Dark Angel”), a quirky veteran medical examiner (David McCallum, “The Man from U.N.C.L.E.”), an ex-Secret Service agent (Sasha Alexander, “Presidio Med”) and a Goth-style forensics specialist (Pauley Perrette).

The interplay among this strong cast makes “Navy NCIS” work, and the premiere does a good job of detailing who the characters are. Sure, there are definitely derivative elements from the shows that it emulates, but original ideas usually can’t be sold to the masses (that’s why there’s cable). This is the familiar executed well.

Fans of either “C.S.I.” or “JAG” will appreciate “Navy NCIS,” which enjoys the now-cushy time slot that “JAG” spent years carving out. Those who don’t see the charm of those two needn’t stop here.

Also premiering tonight is a charming romantic comedy, “I’m With Her,” at 8:30 on ABC.

Loosely based on creator Chris Henchy’s relationship with Brooke Shields, the series tells the story of how high school teacher Patrick Owen (played by David Sutcliffe, “Gilmore Girls”) meets movie star Alex Young (Teri Polo, “Meet the Parents”) and how the couple from two different worlds fall in love.

The pair’s relationship has to overcome obstacles: his intrusive best friend, her cynical sister, him being uncomfortable in the world of celebrity, her being uneasy in the halls of academe.

Sutcliffe and Polo enjoy a nice on-screen chemistry. But “odd-couple”comedies have been done to death, so the challenge for writers Henchy (“Spin City”) and Marco Pennette (“Caroline in the City”) is to keep their material fresh. That will determine how long viewers will be with “I’m With Her.”

Also premiering tonight, but not reviewed, is “One Tree Hill” at 9. It’s the WB’s attempt to find a replacement for the retired “Dawson’s Creek” in the suburban-teen drama category.