There's Jack Paar! He's standing at the other end of the platform at the New Canaan, Conn., commuter train station and looking only a shade older than he did two decades ago, when he quit as host of NBC's "Tonight Show" after five hilarious, tempestuous years. Paar is wearing an open jacket and a bright red sweater and has his arms outstretched; he looks like he's going to grab the first woman passerby he sees and tickle her until she cries.

Paar always had a knack for havoc. He was trouble, in one of the better senses of the word. Now he has momentarily banished himself from exile and returned to the public eye for the most prosaic of reasons: to promote his new book, "P.S. Jack Paar," a jaunty, pugnacious memoir that is as funny, spleeny and disorganized as the man who wrote it, a man who claims he is no less satisfied tending a tidy garden and visiting neighbors in Westchester County than he was as a national sensation, the king who ruled the night and made his own personality a hotly debated public issue--like, say, acid rain.

"I think I'm always interesting; it's a delusion I've had for years," says Paar, who looks very comfortable behind the wheel of a brown 1980 Rolls-Royce Silver Shadow recently given him by his wife, Miriam, and daughter, Randy, now married and a successful Manhattan lawyer. Although he continued at NBC with a weekly prime-time television program for three years afterward, Jack Paar really left the epicenter of the maelstrom when he handed the "Tonight Show" scepter to Johnny Carson in 1962. A party was over, one that still had plenty of rowdy laughs left in it.

In a fame-crazy society like ours, people find it hard to believe that Paar, who never bothered hiding his hamminess, isn't dying to leap back into the limelight. He's been asked about it so many times, he can now ask as well as answer the questions himself. "Am I coming back? Nooo!" he says. "Do I want to come back? Nooo! Will I? I can't imagine how." Does he miss it? "No." But he was so happy doing it! There is a long pause. "Was I happy doing it?" he asks. He doesn't seem to remember if he was happy doing it or not. But he looked happy doing it, happier than anybody else who's ever done it.

Soon after Paar's recent reemergence, somebody floated a rumor that NBC had made him an offer to take over the critically ill "Today" show. The rumor was then shot down. But Paar says, "It has been discussed. It was with a very minor person" at NBC, and discussions never got very far. Paar's tennis pal Gene Jankowski, president of the CBS Broadcast Group, offered Paar $20,000 a week to be himself in front of a camera again for CBS Cable, Paar says, but Paar refused and CBS Cable folded last year. "I think the idea of talking to people is kind of over," says Paar.

People may remember the Paar years only for their tumult; Paar fought and feuded with columnists, fellow entertainers and, after a moving program from the Berlin Wall that included allegedly excessive participation by Army personnel, the U.S. Congress (Paar won, Congress lost). But in Paar's hands, "The Tonight Show" became the whole country's Algonquin Round Table. His guests were wits, zanies and bon vivants; many told richly amusing stories, and so did he. Jack Paar got under America's skin. In "Understanding Media," Marshall McLuhan marveled at Paar's uncanny rapport with the camera; no one, ever, has made conversation on television more entertaining.

"I tell you, I am good at chaos," Paar says. "If there's another war, they should call me." Paar was the Caruso of talk. He made it a performing art, like singing or dancing. The footprint he left on the cuckoo-bird moonscape of television is enormous. Many people were appalled at his emotionalism and the thinness of his skin, but fans forgave him the way they'd forgive an Uncle Harry or some other member of the family. Jack Paar was the original Mr. Warts-and-All.

Of the million memories of Paar's manic reign, one might recall the night he looked into the camera and growled, "Ed Sullivan is a liar" (during a silly feud with Sullivan over access to stars) or, the time he told Elsa Maxwell her stockings were crooked and she said, "I'm not wearing any," or the fact that on the day Oscar Hammerstein II died, Paar invited Patricia Neway, then appearing in "The Sound of Music," on the show to sing "Climb Ev'ry Mountain" in memoriam. Paar's last "Tonight" show, on March 29, 1962, featured filmed farewells from such celebrities of the time as Robert F. Kennedy, Richard Nixon, Tallulah Bankhead and Billy Graham, and one from a member of the production crew, who talked about how Paar arranged camera appearances (and thus a mandatory $320 payment) for people on the staff who were having financial problems. The engineer said, "Jack, your heart is bigger than your bag of tricks."

There was nothing like it. There was nobody like him.

PAAR CLAIMS now that what he wants is to be left alone. "I spend most of my time avoiding people," he says, and the welcome mat to his airy, spacious New Canaan home grumps, "Go away." Why, then, did he write a book? He says it was "fun," that he's already well into the writing of another one, that he enjoys telling stories--but he doesn't articulate what is probably the main reason: the fear of being forgotten. When he makes a rare public appearance now, he'll tell young people in the audience, "I'm the fellow who used to entertain your mothers and fathers late at night. Obviously, I didn't do a very good job, or you wouldn't be here."

Jack Paar's momentary reappearance can be thought of as "Return of the Jedi"; he's come back with light saber flashing. He is one man who hasn't mellowed, who proffers no confessions or apologies. Among the disputes he ignited upon resurfacing, almost as a reflex action, is one with Carson, or at least with Carson's producer Fred De Cordova, who mysteriously canceled a scheduled guest shot for Paar on "The Tonight Show." The alleged grounds were that Paar had promised a limited exclusivity to the program, then appeared on too many other shows, but that doesn't sound too plausible for a show whose regular guest list is clogged with dregs like Bert Convy, David Brenner and George Segal. Are they kidding?

"I don't know the reason," says Paar. "But I'm just as glad. If it's going to be a confrontation--it is possible that I talk a lot, and maybe that's the reason." Paar won't be goaded into saying unkind things about Carson, except indirectly; he will at least concede the program now is something less than what it was under Paar.

"When it comes to 'The Tonight Show,' it's changed, from what was once a kind of an eclectic show with authors and crazy people like Charley Weaver and Dody Goodman, people like that," Paar says. "It primarily was a more literate show than it is now, I would gather. We had news people and presidents and vice presidents and senators. Now it is--all the talk shows are the same. They now are all putting on stars from situation comedies who aren't stars. Now when I say 'stars,' a star to me was George Jessel; I'm talking from the bottom up. But these were men of background--the theater, vaudeville, war experience. Even Jessel had a fund of stories. Now they bring some guy out of a Texaco station and in a week he's a star on some show called, you know, 'Hilliard's Poopoo.' And he's on the cover of Time magazine and suddenly they're interviewing him. And the kid has no background, no history, nothing.

"Dorothy Parker, George S. Kaufman, James Thurber, Oscar Levant--these are the people I had on." There will be no Paar retrospectives including footage of such people, however, because NBC, says Paar, "didn't save any of it. Nothing saved. Embarrassing. Embarrassing. NBC screws up everything." NBC burned the Paar footage years ago to conserve storage space.

Paar says he won't knock the medium of television because it was so good to him. But he also says, "I can't say anything bad; I don't watch television. It's easy not to watch. If I were a television personality or an executive of television, I would be concerned with how quickly you can get out of the habit of watching television. I mean, we thought it was so important in our lives. I can tell you, in a few weeks, you just stop watching, and it means nothing.

"What do I watch? I loved 'Brideshead Revisited' for some reason. In my book, I compare that family to the Kennedys, and you know, nobody else has pointed that out, how much they're alike, and I think I should get some credit for that. Television, it was good to me. Look what I got, look how I live. It's hard for me to knock it. But I don't watch. Now, what am I supposed to say after that? I watched a little bit of 'Winds of War,' but I like everything people don't like. Like I tuned in to see it just because I love Ali MacGraw! And I'm the only one! I just love Ali MacGraw!"

A BRIGHT yellow skylight drops a puddle of color into the back room that Paar converted from a sun deck at his New Canaan home. In the yard there are tennis courts, a jungle of foliage and a pool that was made to look like a swimming hole. "Five and a half acres, and no lawn," boasts Paar the happy homeowner.

On the walls of the house, pictures of Paar with such long-gone luminaries as Albert Schweitzer, and a Time cover portrait of him. From nearby, Paar's neighbors, Floyd Kalber and his wife, Betty, come by for lunch; their appearance starts two of Paar's four dogs, a dachshund and a German shepherd, yapping loudly. Kalber was top man in Chicago news at the NBC-owned station there for 16 years, then went to New York for a short stint on the "Today" show. Paar says NBC gave him a raw deal, but Kalber, dressed in a blue jogging suit and puffing a pipe, looks eminently prosperous and says he still works now and then.

The Kalbers and Miriam Paar settle into chairs in the back room and become what Paar still loves, an audience. No one laughs louder at Paar's stories than Miriam, who's been laughing for 36 years of marriage. Once during a story, she refers to her husband as "Jack Paar," as if she barely knew him. She was with Paar during his abortive movie career at RKO, his many attempts to find a niche on CBS, the hectic nights of "The Tonight Show," and Paar's short-lived, unhappy return to TV in 1973 as the host of an ill-conceived late-night show on ABC. Paar calls Miriam "the great thing in my life." In his book, Paar scotches the longstanding rumor that his wife, whose maiden name is Hershey, is heir to a certain chocolate fortune. He also says he made a mere $500,000 a year as host of "Tonight." The Paars are able to live well now, he says, because of "wise investments" he made then.

How does it feel to be back? "Going on shows is a real pain in the ass," Paar says. "The only good part is, if I could say this modestly, the respect I have of my peers. I mean cameramen, stagehands who remember me, and that is warm and touching and grabbing and hugging and I didn't know that that existed. I haven't known that for 10 years. And secretaries at NBC the other night--they go home at 5:30 or 6, but they waited to see me in the lobby. These are secretaries that I worked with! I'd forgotten their names and they now have gray hair. But that part was touching."

Not so touching for Paar was a week-long series of interviews on "The CBS Morning News," he says. He felt he was "used," objects to the way the interviews were edited (a camera zoomed in when Paar, once notorious for being an easy weeper, teared up while discussing the death of his mother) and says CBS brought so much equipment to his home that "they blew all the fuses." But he thinks Diane Sawyer, coanchor of the program, is the kind of "phenomenon" that happens only "once in 10 years" and says of her, "That girl is a class act, and that's what that girl is."

Paar wouldn't go on the "Today" show, he says, because "there's nobody in charge" of it on the air, and he refers to Jane Pauley only as "the girl," one who is "so concerned with her hair I'm afraid she doesn't have time to work in the news." As for Phil Donahue, on whose talk show he appeared, "I was not terribly impressed by him." He also dropped in on Merv Griffin. "Just because Merv can stutter, he thinks he's me. And Merv's losing stations. I think he's down to 60. I'm sorry, because it was the one fun show to go on. Merv is wonderful because he really is like a fan--he's one of the early kids who hung around--so when I got there, it's just putty; I can do anything I want."

Merv likes to tell this story about Paar: Once he and Paar were walking down a hallway at NBC when Paar spied a man leaning against a wall, became very agitated, took Merv aside and said, "Who is that guy, that guy over there? He's been following me for weeks now. I see him everywhere." And Merv said, "Jack, that's your saxophone player! He's been with you for three years!" Paar laughs and says, "I think that one is true." PAAR'S reminiscence tends to be of the scattershot sort. Occasionally he will interrupt himself with a "Who are we talkin' about?" or "Where was I?" or "Are we talking about Berlin or Cuba?" One minute he will say "My short-term memory's not good" and the next, "I have total recall." In the book, Paar even forgets one thing about "The Tonight Show." Hugh Downs, his announcer, did not say "Heeere's Jack" as Ed McMahon says "Heeere's Johnny." No no no. Downs would say, after listing the guests and himself, "And now," allow a dramatic pause, and then, "Here's Jack!" Then Jack Paar would come out and invent television.

"I'm amazingly healthy since I had that prostate operation," Paar says, beginning what amounts to a ramblingsoliloquy. "There's factors in my blood that indicate longevity. I said to the doctor, 'I have a problem.' He thinks impotency, see, which isn't a problem. I mean, how much is one to expect?" A roar from Miriam and the Kalbers. "But anyhow, he said to me, 'We'll discuss it later, drop your pants and cough, and lean over' and everything, and I said, 'Look, Doc, what I'm talking about is, I have a fantastic memory, everyone knows about it, but I'm worried. I don't know where my car keys are. I don't know what car I have. What am I doing in Greenwich? I thought this was Westport!' And I'm really concerned, and I told him I go to this health food store and buy all this stuff for memory, and should I buy it or not?

"He said, 'Later, later.' So as I was leaving, I said, 'Memory, Doc!' He got a prescription blank and wrote something on it. Then I leave and go to the drugstore and on the way I open it. It says, 'For memory: Make notes.' "

Screams of laughter all around.

"I want this to be good," says Paar eagerly to the interviewer. "Here's an anecdote I never used. At the height of the Sullivan feud, which he started, my daughter, Randy, came to me and she said to me, 'You're a religious man, Papa?' I said, 'I'm trying to taper off on religion.' Religion is a lot of--I just can't. So anyhow, she said, 'The Bible says you should forgive your enemies,' and I said, 'Well, that's not a bad idea, what the hell?' And she said, 'Papa, you don't forgive your enemies.' And I got a little angry and I said, 'Now Randy, what is this bit?' She said, 'Pop, you should forgive Ed Sullivan.' I said, 'Why should I?' She said, 'Well, I would like some tickets for the Beatles.'

"Now most people would let the story end there. That night, I'm on the air. I tell exactly what happened. The audience loves the story, loves the fact that I was willing to make myself an ass--in most of my stories, I'm really the ass, the joke, the patsy--and, you know what happened? Four tickets came over from Sullivan the next morning. For the Beatles. Front row. And you know who Randy took? Julie Nixon."

A chorus of "Awwww" from around the room.

"Here's a funny story," Paar continues, sipping champagne as he and Miriam do every morning at 11. "This one I've never used. We change our phone number a lot here because it gets out and some nut calls. So I called the phone company one day, and I said to the lady, 'I'm a public figure and I have a lot of crazy calls, would you please change my number?' 'Oh sure, Mr. Paar.' And I said, 'Now, could you give me a rather chic number, I mean a number that's kind of cute?' And she said, 'Well, here's what's available,' and she reads them off to me, and she gets to something like, oh, 1-1-1-2. Well, I said, 'I like that, I'll take that one.' She said, 'Okay, Mr. Paar,' and boom. Now that number obviously belonged to somebody before." He pauses. Looks around the room. Then springs it: "Westchester Emergency Weekend Plumbing Service! Jesus Christ! And I called and I said, 'This isn't fair!' And she said, 'But you liked that number.' Can you imagine what Saturday and Sunday was like around here?"

Everybody is chuckling but good by now, and one and all chuckle on and on, even through stories Paar has told before. It is suggested to Paar that one of the reasons he was so good on television is that it really makes no difference to him if he is talking to four people in a room or 20 million people watching on television. He says, "Same thing. That may be the only talent I have, is that I am able to do that."

In his book, Paar talks about the old "Tonight Show" regulars, including Genevieve, who pronounced his name "Zhockpah" and who is now married and living in suburban Washington; Jonathan Winters, who was never funnier than he was on the Paar show, and the late Alexander King, among others. He writes, "I was ready for fame when I was six years old," in his native Canton, Ohio. He tells stories about his heyday, driving through Hollywood with Judy Garland and spotting Elvis Presley in the next car at a stoplight; says of Groucho Marx, "He bored me," of Humphrey Bogart that he was "a boor" and of Marilyn Monroe, with whom he appeared in the film "Love Nest" when both were unknowns, that she was "a sad, shy, arrogant loner."

PAAR PICKS a few new fights in the book, one of them with Steve Allen, whom he chides for supplying the hosts of shows on which Allen will appear with pretentious encomiums to himself, then acting surprised when he hears the praise. "You know, the last time I saw Steve, I hugged him," says Paar. "It was at the Carol Burnett testimonial. And I said to him, 'I understand you're writing another book on comedy,' and I'd heard he didn't know much about Frank Fay. I said, 'Well I knew him very well and if I could help you--' And with that, this is Steve, he whips out a tape recorder, he's so pompous, and he says, 'I'm talking to Jack Paar at the Carol Burnett show. He has just informed me that he has information on Frank Fay. Jack, would you give us . . . Jack, where can I . . .' This is in the middle of a dinner! 'This is Steve Allen. File this, 71493.' People look at him; they think, 'This man's crazy!' And he never did call me.

"I remember, even when he was a hit, he was a pain in the ass. He was the kind of a guy who'd come into a room and right away he had a terrible headache and you had to get Empirin. Everybody had to get Empirin. And the next time, he had a button coming off, and everybody had to run and get a button and sew. He always had that kind of crisis. And he was always moody. He acted like a genius. I think he is, what is the phrase, a legend in his own mind."

Paar also gores Joan Rivers, the wicked witch of comedy. "I called her--what did I call her, honey?" He is asking Miriam. "Oh, the Albino princess, because she looks so white. She's a monster. I think it's just awful. If you want to have Joan Rivers on 'The Tonight Show,' why not go all the way and just get Charles Manson? Have 'The Degenerate Hour.' "

Then, "Oh!" says Jack Paar, "I've got a great story I'm gonna tell you in a minute." And so the afternoon, and a cheerful lunch, goes. Occasionally Paar is reminded of things about "The Tonight Show" even he seems to have forgotten, like the way he would go through phases of having a favorite song, and every singer who came on the show had to sing "Till There Was You" for a while, and then "The Party's Over." Reminded of that, Jack Paar smiles and says, "Yeah. I would cry."

He was always the most self-deprecating of personalities--he would revel in detailing humiliations for the TV audience--yet he also seemed, and still does seem, utterly and grievously pierced when ridiculed by others. He will tell a great story on himself, like about how he tried dyeing his sideburns to look younger for last week's appearance on "Entertainment Tonight" and broke out in a terrible rash that Miriam could control only with the dogs' flea powder, and then he will bemoan the way a Chicago reporter spent a day with him there, impressed him as being terribly friendly, and then wrote a story he considered mean and unkind, fixating on his weepiness and hairpiece. It's the word "egomaniac" that hurts him the most, he says; in fact, when it is spoken aloud over lunch, it seems to take the shape of an arrow aimed at his heart.

"I hate that word, I really hate it," he says. "I hate it more than anything. Journalists make me an egomaniac because I know that when they come here--you didn't come to talk about the dogs. I must say, they do use that word about me a lot. They use it all the time. As a matter of fact, they use it even when they like me. So listen, it must be true. If you all say it."

There follows a chorus of "No, Jack, no," the thrust of this being that it's not true at all, and Paar looks healed by this. Egomania really isn't the word for him. Even into his sixties, what he still has is a childlike sense of discovery about himself, this amazing creature, and the big wide world around him, a world that he admits he now really hides from most of the time. "In a way, yeah," says Paar. "Now--that's a good angle; you can use that. Yeah, I would say, the less I have to do with the world, the better."

JACK PAAR'S moods change like the sun that comes through the yellow-bubble skylight and on this day is continually being undercut by clouds. He doesn't stay gloomy for long. There is another story just around the corner--a recollection about meeting Schweitzer in Africa, or learning that LBJ's gall bladder is kept in storage at the National Archives, or seeing Ethel Kennedy throw a glass of wine in a dinner guest's face. "Every word," Paar used to pledge, "is true." He says he's happy the promotional appearances for his book are almost over; he turned down several interviews. One night, he made a surprise cameo on the David Letterman show, but says he won't do a guest shot there because the audience is too young to remember him. Letterman invited him again, on the air, just last Monday, when Dody Goodman was a guest. Letterman's director, Hal Gurnee, was Paar's director for years, Paar says proudly. Letterman has said Gurnee often keeps the cast and crew entertained with old Jack Paar stories.

"When I die, and you wanna write something good, go to Gurnee," says Paar.

But--factors in Paar's blood indicate longevity, remember?

"Well, then, if he dies, come to me," Paar says. He turns to Miriam. "I was funny on Merv the other night, wasn't I?" he asks her, and Miriam says, "Yes, Jack, you were very funny." The dogs bark. The sun shines. And now--here's Jack!