TV fans are bidding a final farewell to some familiar faces this season, as many mainstays of the small screen fade to black.

Ally McBeal, The X-Files, Felicity, and Once and Again are among this season's canceled shows that had once been the subject of fervent water-cooler talk and industry buzz. And others like Just Shoot Me, Spin City and ER, while still popular, are showing signs of age.

"Ally McBeal was a real pop-culture touchstone and that has faded. Felicity was also going to be the next big thing and it's going off air," said Ken Tucker, critic at large for Entertainment Weekly. "ER is suffering staleness and has lost a lot of the cast that made it famous."

The disappearance or decline of these old standbys also has TV executives scrambling to create the next breakout hits.

"There's a constant changing of the guard in TV and that's what makes it watchable," said Bryce Zabel, chairman and CEO of the Academy of Television Arts and Sciences. "It's like the ocean tide: There are times when the swells are huge, and times when they are more modest. This year there will be more change than in some other years."

Networks like ABC, CBS, Fox, and the WB face some big prime-time holes in their schedules next season. And even NBC, which announced its fall schedule yesterday and has a relatively stable lineup, is trying to boost interest in new shows — especially because the No. 1 show, Friends, has only one season left.

"In general, sitcoms are in trouble. The format is beginning to show signs of strain," said Tucker. "Long-running shows like Spin City, Dharma & Greg and Drew Carey are getting tired. Everybody Loves Raymond is the last successful sitcom to come along."

Even proven stars are no guarantee of success. Programs starring Ellen DeGeneres, three of the Seinfeld alumni, superchef Emeril Lagasse and actress Joan Cusack have all failed in recent seasons.

"The Education of Max Bickford has two Oscar winners — Richard Dreyfuss and Marcia Gay Harden — and there's a big question of whether it will be renewed," Tucker pointed out. "James Garner in First Monday has done badly and [the show] will probably be cancelled."

Instead, new shows with unfamiliar faces and original concepts are catching on with viewers.

"Look at Alias. That made a star out of Jennifer Garner, and Smallville made stars of complete unknowns," said Tucker. "And shows like 24, Baby Bob and Bernie Mac with new forms have become hits."

Zabel, who has written for TV series including L.A. Law and Lois and Clark, said this kind of upheaval is par for the course in Hollywood.

"There's always a tug-of-war in TV between old forms [and new ideas]," he said. "Anything done over and over wears itself out. It encourages people to experiment with content and form of the shows. And those are the hits you're looking for."

Baby Bob, a sitcom featuring a talking baby, is perhaps the best recent example of an unexpected success, said Tucker.

"[Executives] thought the American public would laugh that off the screen, but it's quite the opposite." The show scored surprisingly well on its debut, almost keeping pace with Everybody Loves Raymond, according to Variety. 

The wide-open field has networks competing more fiercely than contestants on Survivor, Tucker said. "There's a lot of pressure on programming people, especially at ABC and at Fox. They have to do a lot of development."

But Zabel said most industry people are excited about getting a chance to develop new shows.

"I've read most of the pilots this year and there are a number of promising series," he said. "The WB picked up one called Everwood, one of the best pilot scripts I've read. Plus, hope springs eternal in television."

Whatever innovations executives try, a show's fate really depends on the viewers.

"Remember, the audience votes. It's a democratic process," Zabel pointed out. "They vote every night of the week."