In the Spin-Off Cycle

Prepare for a new golden age of spin-offs. not since the '70s, when The Mary Tyler Moore Show begat Rhoda and The Jeffersons and Maude sprang from the fertile loins of All in the Family, have network execs been so busy dismembering their hit casts in search of new TV shows.

Teen power is the force behind this latest spin-off frenzy, and at least for Beverly Hills 90210, it's happening just in time. With the current cast almost at the Social Security halfway point, Aaron Spelling may eventually graduate what's left of the original cast to make room for a new class of West Beverly High.

A Party of Five spin-off will be trickier to pull off, since the Salingers would be real loners without Jennifer Love Hewitt's Sarah. Yet in the tentatively titled Time of Your Life, Sarah ditches the orphaned quintet to track down her biological father in New York and may engage in tortured relationships with someone other than Bailey. ''The execution will be crucial,'' says Steve Sternberg, a senior partner with TN Media. ''She probably can't carry the show alone but combined with a reasonably strong cast, it could do well.''

Spells Trouble, the Sabrina, the Teenage Witch spin-off, will be introduced during Sabrina's Feb. 12 episode, showcasing two preteen witches (played by Sabrina star Melissa Joan Hart's younger sisters, Emily Hart and Alexandra Hart-Gilliams) who lose their powers after their mother falls for a mortal. ''It's more about a family's relationship than magic,'' says creator/mom Paula Hart.

Fighting evil is on the bill for Buffy the Vampire Slayer's Angel (David Boreanaz), who's to star in his own WB drama about L.A. demons. (And they're not in the biz.) ''With Buffy and Sabrina, there's a universe that lends itself to mythologizing,'' says Joss Whedon, Buffy creator. ''That works in a spin-off.''

BEST-CASE SCENARIO
A mega-crossover in which Angel and Sabrina battle Hewitt for Bailey's affections.
WORST-CASE SCENARIO
We get Dawson's Puddle.