SAN DIEGO – Morgan Fairchild and Bo Derek have been going at it for hours.

On an otherwise quiet Saturday night, there seems to be no end to the yelling, face slapping, hair pulling and hurling of vases full of long-stemmed roses.

Then Fairchild grabs Derek by the throat as she gasps for air. The director yells “Cut!”, we presume in a good way.

This sort of warring is typical on Stage 3 at Stu Segall Studios these days.

Yet tonight, it’s the mother of all cat fights. By 10 p.m., even assorted “antiques” and a couple of paintings have succumbed to the fury.

And some time around 4 a.m., it will all end deliciously in multiple layers of white butter cream as the raging rivals tumble into a towering wedding cake.

Just a taste of the melodramatic madness arriving Sept. 5 with the launch of MyNetworkTV, the Fox-owned upstart created for those WB and UPN affiliates left orphaned when their networks merged into a new venture known as The CW.

Each weeknight at 8 p.m. EDT, MyNetwork will present a pair of one-hour serials or “telenovelas” – “Desire,” which follows the saga of two brothers in love with the same woman, and “Fashion House” – lots of beautiful women on the runway and others in fabulously staged cat fights. Other networks have similar projects in the works.

The MyNetwork shows will air Monday through Friday, with a recap episode on Saturdays, and conclude after 13 weeks, when a fresh pair of novelas will take their place.

Those shows are already in production at Segall Studios – “Watch Over Me,” a dramatic love story a la “The Bodyguard,” starring Casper Van Dien; and “Art of Betrayal,” with Tatum O’Neal starring as a lover scorned.

“With the way that the world has been going, this is hitting exactly at the right moment,” said Fairchild. “People are going to want to tuck the kids in and sit back and watch a couple of blondes bitch-slapping each other across the screen. What could be more fun than that?”

Derek said the rigors of filming 65 episodes in less than four months is “insane.”

“But my character is so much fun to play,” she said. “She’s just evil, and that’s what intrigued me.”

Adapted from the wildly popular Spanish-language genre, MyNetwork’s telenovelas appear, – at least for now – to lack the cultural depth and sexual passion of the originals.

But the shows will follow the same finite format – self-contained stories with a beginning, middle and happily-ever-after end.

“What makes a novela unique is that there is an ending and a sense of urgency when you watch it,” said Twentieth Television’s programming chief Paul Buccieri.