The television airwaves will soon be full of new looks for old familiar faces.

In what seems to be a growing trend, TV execs are mining old shows for beloved characters from days past. Starting in late April and continuing through the May sweeps, the networks will be chock-a-block with reunions, behind-the-scenes shows, tributes and other nostalgic programming.

Mary Tyler Moore, Bill Cosby, the gang from Cheers, the cast of L.A. Law, the stars from Laverne & Shirley and even the folks from That's Incredible will all return to the small screen in what is the biggest plan to score ratings since reality TV hit the airwaves.

"People will definitely tune in to reunion shows. They are remembering their youth, recapturing their youth," predicted Vincent Terrace, author of several pop culture books, including the Sitcom Fact Finder series. "People like to see what happened to their favorite star, to see what they're doing now and to maybe get some dirt on what happened behind the scenes."

Judging from past attempts, the networks may well get their viewership boost. CBS's Carol Burnett retrospective last November pulled in 29.8 million viewers, far exceeding the network's expectations for the program.

"That was a smash — and that was just clips of her shows," said Terrace. "That's what started the whole thing."

NBC, in celebration of its 75th anniversary, has scheduled the most celebrity appearances. Among them are the reunion of The Cosby Show, a Must-See TV special and innumerable guest appearances on current shows.

Quincy's Jack Klugman will be on Crossing Jordan, Melissa Gilbert will appear on Providence, some cast members of St. Elsewhere will guest star on Scrubs and Carla, Norm and Cliff from Cheers will pay a visit to Frasier.

"Nostalgia has always been part of pop culture and TV is a big part of pop culture, so I think [the programming] is natural, " said Jeff Gaspin, executive vice president of specials at NBC. "There is an emotional connection people have with these stars, with these people they knew from when they were the ages between say, 12 and 20."

CBS announced last week its own retro special: A Mary Tyler Moore reunion to air May 13. It will reunite Moore with her famous co-stars Ed Asner, Valerie Harper, Betty White and more.

Mary Tyler Moore is one of the heaviest hitters for sweeps. The groundbreaking sitcom, which aired from 1970-1977, represented an era of change in television to many viewers.

"That show went off the air, what 25 years ago, but anyone who watched it will remember fondly what they were going through then," said Bruce Zabel, chairman of the Academy of Television Arts and Sciences. "It gives you a chance to look back at your life as much as on the lives of these characters."

And that's the key to nostalgia programming. Whether it's seeing Susan Dey and Harry Hamlin rekindle their on-screen L.A. Law romance, hearing Penny Marshall and Cindy Williams reminisce about the wacky shenanigans on the Laverne & Shirley set or watching John Davidson, Cathy Lee Crosby and Fran Tarkenton introduce old clips of That's Incredible, audiences tune it to see their old friends.

"When a show goes off the air, it's as if close friends moved out of town, and you haven't seen them in a long time. Or it's like going to a high school reunion," Zabel said. "These were your best friends, and you want to catch up.

"You may not be able to go home again, but viewers seem to like it when TV gives it a try."