Tony Danza has cashed in his one-way ticket to Polookaville for a free ride on Cloud Nine. Oh, he hasn't been on the cover of People magazine yet, and with uncommon tact he has yet to record an album of original songs by himself, but this 25-year-old ex-fighter from Brooklyn has been picked off the canvas of the boxing ring and dropped inot the cast "Taxi," the only intelligent comedy show on ABC and one of the new season's biggest hits.

And he has embraced this stroke of luck and pluck with the most engaging and upfront kind of optimism, gratitude, naivete and terror.

"I keep waiting for somebody to say, "Hey, we're kidding,"" says Danza in a voice that invokes the spirit of Huntz Hall. "I mean, I'm just beginning to feel almost, almost, ALMOST like I deserve it, like I should really be there. But let me tell you, I still sort of expect them to wake me up at any moment and tell me I'll have to go back in the ring."

Danza fought 11 bout as a professional and many more as an amateur before fate waltzed in and got him a screen test. Somehow this "unbelievable chain of events," as he describes it, was set in motion by "an over-the-bill hooker who wanted to be my manager. She latched on to anything that had potential in a gym - which meant, like you know, a suit."

But when a producer friend saw Danza he alos recognised potential. Ther's something completely unspoiled about him - so that whether or not he can "act" is irrelevant, even on the best-cast and best-acted new show of the year.

He did take acting lessons. Actually, acting lesson. "My manager says to me, "Tony, you gotta get an acting lesson." He said there was a teacher right around the corner from Gleason's Gym where I worked out. So figured I'd try it, what the heck, I leave Gleason'son 29th Street and go up to this place and meet the teacher, who had, I swear, the most relaxing voice I ever heard. I mean it was like hmmmmmm - hey, I can't even do it.

"So there are all these people rolling their heads around and lying on the floor and going crazy. I mean, Belleveue comes in and they'd take the whole lot. And the teacher starts this exercise where he says, "Relax, let each part of your body drain of tension," and we're all lying on the floor by this time and, well, I fall asleep. I swear. Right asleep. I mean, I just dozed, but when I woke up I didn't know how long I'd been asleep or whether everybody would be sitting there in their chairs looking at me alone on the floor, or what."

That was the end of Danza's formal instruction in the thespic arts. Just as well - he doesn't need it. Untrained journalists make fortune in TV news because they come across as authoritative and comforting on the air; actors are welcomed into millions of living rooms because they appear personable and decent. Danza is instinctually eager to be liked. He cannot fail. His fans mail at Paramount has just crossed the 100 letters-a-week thresh-old and secretaries at the studio say more and more girls are calling up to ask about him.

"My big dream," Danza says confidingly, "was to be a popular guy. Sveringly, "was to be popular guy. Ever-they see you. My big ambition was to walk down Fifth Avenue like it was, you know, The Neighborhood. So, now, I'm getting a shot." He hunches forward in his ABC chair, wrings his hands and smiles like you when it looks like rain but you have planned a picnic and hope for thw best.

On the program - a beautifully writen team comedy seen Tuesday nights on Channel 7 - Danza plays Tony Banta, not coincidentally a semipunchy boxer who, like the other characters in the show, is temporarily waylaid in the rustic purgatory of the cabbie's life, waiting for something better to come along. Like maybe a big break.

"I used to think I was born to be a boxer," Danza says. "It's gift, too. It really is. I was good at it. I could been somebody. I could have been a contender." He is perfectly serious.

"I was always fighting when I was growing up. I was constantly in fights. In car, somebody would say something, I'd say something, and I'd get in fight. It felt good. Which is bad. I enjoyed fighting - what can tell you? I got into boxing as a lark, but I did have a great right hand. When boxed as a light-heavyweight, I knocked out the first five guys I fought. But I didn't really know how to fight."

Still, one does learn certain talents on the streets. "I was a hoodlum in Brooklyn," Danza says of his youth. "I used to be in trouble all the time. Of course, the things I got suspended from school for you wouldn't even get reprimanded for now. Cutting class was a big deal then. Now - nothing. The worst thing I ever did?" He doen't want to say. "The worst thing I ever did was get a tattoo in Lake Geneva, Wisc." He was 20, it's a picture of Mr. Natural on his right arm, and he hates it.

Danza does not feel embarrassed about the violence of boxing. "Sure, it's pure violence," he says, "but it's also an art. There's something beautiful about an unimpeded punch landing on a chin." When it's your chin, however, and the unimpeded punch lands on it, and your mother or your father is sitting in the crowd, and you can hear your mother, born in Sicily, "shouting and screaming," and your father, born near Naples, looks "as you catch glimpse of him, you start to develop doubts anout the art of the ring.

Danza found others ways to make a living. "I washed dishes in temples," he recalls. "I was even a cab driver for a while." He got a B. A. from the Universitu of Dulbuque and because "I love to work with kids," thought of becoming a teacher.

Now this acting thing has him hooked. And the ring at least knocked all fear of crowds out of him. "You know, "Tony Danza" at Irish Night just doesn't make it," he notes, recalling the boos when he'd have to fight an O'Somebody in green truncks. "But audiences at those shows are not hostile. They are dying to laugh, dying to be entained."

He wants to send money home, to his own separated mother and father on "The Island," meaning Long Island, and to a 7-year-old son by a brief marriage living in Chicago. "We got in trouble," he says with his eyes to the floor. "If you want to put that down, okay, put that down. I was brought up Italian and righteous and taught to do the right thing." So I get married, I gave it a shot for four or five months. The girl and me, we're still good friends."

Hey. You know. Whaddayou gonna do?

"I don't know what I want to do now," Danza says. "I just want to play it by ear. I really want to be a good at this, I want to make a mark, I guess, I guess, I don't know - maybe I'm listening to too many crazy people.

"I don't know what I want out of it To be "a star"? Is that the deal? My cousin Tony, he says to me, "Tony, don't go out there to Hollywood just to make five ar ten thousand bucks a week. Go out there to make a mark in history. Go out there to be somebody." Who? "Well, he mentioned John Wayne." Danza grins. "I'd like to be a great actor, like (Robert) De Niro, or a great humanitariam, like Jerry Lewis." He is still perfectly serious.

Danza recently coached De Niro on boxing technique for De Niro's role in "Raging Bull," based on the autobiography of Jake LaMotta. And a "Taxi" episode which featured Danza and professional fighter Carlos Palomino as guest star was considered so good by the executive producers that theu moved it up from fifth show aired to second show aired.

But the real pleasures are the bounties of success - a small house in the lower Hollywood hills, a hot car ("I want an old "Vette, '65 or '67) and a place to put it on the Paramount lot.

"You know what I got?" he says with the excitment of a lottery winner. "I got a spot! For my car! Yeah, with my name on it!" He looks so innocently and earnestly delighted by this that you hope he'll never have to see the canvas in close-up again.