By ELLEN GRAY - Knight Ridder Newspapers
Date: 02/04/00 22:15

It's a law universally acknowledged in Television Land:

For every Mary (the slim, beautiful one), there must be an equal and opposite Rhoda (the wisecracking, slightly zaftig sidekick).

Oh, "The Mary Tyler Moore Show" wasn't the first to bring together a Mary and Rhoda. "I Love Lucy" pioneered that pairing two decades earlier with Lucy Ricardo and Ethel Mertz.

But Mary Richards and Rhoda Morgenstern's peculiar chemistry has become engrained in the culture, so much so that one of the funniest scenes in the 1997 movie "Romy and Michelle's High School Reunion" featured Lisa Kudrow and Mira Sorvino arguing about which of them had been "the Mary" and which "the Rhoda" during their teen years.

As if.

Nowadays, Rhodas aren't absolutely required to be heavier than their Marys (or if they are, it may only be the ounces of difference required to distinguish between a Size 2 and a Size 0). They don't even have to be funnier.

All that's required for a Rhoda to be Rhoda is a Morgenstern-ish devotion to the proposition that all Marys are created equal. And that Rhodas aren't.

Consider these prime-time Marys and Rhodas:

"Ally McBeal's" Ally (Calista Flockhart) and Renee (Lisa Nicole Carson). Ally, the skinniest of Marys, is frequently outmatched by the most assertive Rhoda ever. Renee, in fact, projects a confidence -- particularly in her own allure -- that sometimes leaves her Mary in the dust. Still, until they change the name of the show to "Renee Radick," she'll always be a Rhoda.

"Buffy the Vampire Slayer's" Buffy (Sarah Michelle Gellar) and Willow (Alyson Hannigan). Buffy may get the best wisecracks, but sad-faced Willow is still the Rhoda by virtue of her dogged devotion to Buffy and all her works. Even her growing knowledge of witchcraft has largely been employed in the service of the Slayer.

"Dharma & Greg's" Dharma (Jenna Elfman) and Jane (Shae D'lyn). One's tall, blond and bubbly. One's shorter, brunette and bitter. Quick -- who's the Rhoda?

"Sports Night's" Dana (Felicity Huffman) and Natalie (Sabrina Lloyd). As the often insecure producer of the show-within-a-show, Dana sometimes out-Marys Mary Richards (although at least she doesn't call her boss "Mr. Jaffee"). Rhoda falls to Dana's assistant, Natalie, by default: While less senior than her boss, she's quicker with a comeback and slightly less likely to worry herself into a frenzy.

"Roswell's" Liz (Shiri Appleby) and Maria (Majandra Delfino). Doe-eyed and luminous, with a lower lip just made for trembling, young Liz Parker is a Mary in waiting, while her harder-edged friend Maria already exhibits a Rhoda-like grasp of life's realities, even in the face of teen-age aliens.