Barbara Walters, the ultimate Welcome Wagon lady, drops in tonight on Kenney Rogers, James Garner, John Ritter and Laurence Olivier in ABC's "Barbara Walters Special" at 10 on Channel 7. Olivier is fascinating, Garner is admirable, Rogers is a bore and Ritter was overexposed long before Babsy every rang his doorbell.

Olivier, saved for the last segment of the show, wouldn't discuss his marriage to Vivien Leigh. Walters says and more's the pity, but he does talk about his difficulties with Maryilyn Monroe, with whom he costarred in "The Prince and the Showgirl." He says she became a different person when she got to the studio -- "thoroughly ill-mannered . . . always, always late" -- and says with more sadness than rancor, "She was so terribly rude to me."

Walters almost badgers the witness when it comes to Olivier's contention that he isn't greatly pleased with himself.

Walters: "Why not?"

Olivier: "I just don't like me."

Walters: "Why not?"

Olivier: "I don't like my own company very much."

Walters: "Why not?"

This control have gone on all night.

Rogers, interviewed first, lives in a 24-room, $20 million L.A. mansion generously toured by cameras while the country-western star, in a voice-over, says lovingly of his wife, a regular on "Hee-Haw," "Marianne, I think, has the most spectacular bathroom I've ever seen." He would appear to be a classical case of success carried to excess, espcially considering even he realizes "I've never particularly felt I was that good a singer."

Walters must be gathering file tape for the orbit department since she asks everybody how they want to be remembered. The gushy Ritter says he wants to be remembered as "a guy who was interested in the golden thread that entwines all of us together." Too much time in the Calfornia sun, perhaps.

But Garner, who has the taste to be a bit embarrassed and reticent about the whole silly celebrity interview business, has the most affable answer to the Walters question. How would he like to be remembered? "With a smile," he says.

These Walters specials executive-produced and directed by Don Mischer, have become very reliable television fixtures; they brighten the video landscape, if sometimes in a daffily gossipy way. Among the many secrets to the success of Barbara Walters is that she consistently stays one step ahead of anyone who might want to satirize her; self-parody is often the best defense.