It's Cosby's Brood vs. the Radical Dude

All of which is probably a roundabout way of saying that Cosby isn't changing his show to beat Bart, he's doing it as a matter of principle. ''I'm working harder and enjoying it more. And whether the audience is there in the numbers or not, I am proud of what we've done.'' Somebody on the set clearly agrees: In the men's room of the Kaufman-Astoria soundstage, the wall bears this scribble: Bart Watches Cos.

Regardless of Bart, Bill Cosby has made radical changes in his show this year. ''I'm re-energized because we have nine new writers,'' he says. ''Four of them are women. (The original three writers, all men, have left.) I think I'm going to get a different voice coming. I felt that women could not only check, as in chess, what the male writers were writing, but could color things in a way that the men never could have thought of.'' The show shot the previous night, for instance, concerned a bachelor party. Thanks to the new women writers, ''the script turned into a good debate, a battle of males and females on what's demeaning and what is not.''

The other big change involves a penniless new member of the patrician Huxtable household. ''To give an uplift to lower-economic people,'' Cosby explains, ''I decided to bring in a 17-year-old female.'' The newcomer is Pam Turner (Erika Alexander), a refugee from New York's Bedford-Stuyvesant ghetto; she's a second cousin once removed of Clair, Cliff's wife, played by Phylicia Rashad. He says Pam — streetwise, angry, and vulnerable — will be a kid with a difference. ''There are certain things you can't do when a child isn't yours. Cliff and Clair are playing with a home-field advantage, but with a disadvantage too. The rules they've set are not necessarily the rules the visiting team wants to play by. It gives us a little extra spice.''

Cosby cannot stress enough his contention that the show's redesign has zero to do with Fox. ''All of the changes made were 'B.B.' — Before Bart.'' Still, the prospect of a battle royal has clearly revivified him at a time when he could easily have kicked back and relaxed. His annual income is estimated at $60 million (a little more than $9,000 per waking hour). And this year NBC reportedly doubled his weekly payments for the show.

His competitive instincts are unquenchable. Cosby may dance in a leisurely fashion in the show's opening credits, but the man at the controls is definitely not ''smoothing.'' He's spoiling for a fight and as happy as the champion athlete he used to be. The Cosby philosophy is best summed up by last year's addition to the cast, the adorable 4-year-old Raven-Symone, who plays Lisa Bonet's stepdaughter, Olivia. Striding into the studio, Raven-Symone lays down the bottom line. ''Okay,'' she pipes up, ''let's make some money!''