CANASTOTA, N.Y. - Aspiring authors are always urged to "write what you know." It thus probably made sense for a struggling actor and screenwriter named Sylvester Stallone to crank out a story about a down-on-his-luck boxer who caught lightning in a bottle and proved to the world he wasn't just another bum from the neighborhood.

Not that Stallone - who will be inducted here tomorrow afternoon into the International Boxing Hall of Fame (non-participant category) - ever actually boxed, but just like Rocky Balboa, the South Philadelphia pug he created, he was from the wrong side of the SEPTA tracks, so to speak, and on an express line to nowhere. The chances of Stallone or his fictional alter-ego ever hitting it big were probably so long that any Las Vegas oddsmaker worth his salt would have made either an off-the-board proposition.

But the low-budget "Rocky," which was released in 1976, won three Academy Awards, including Best Picture, and established a film franchise that, as they say in the industry, has very long legs. Maybe the closest thing to "Rocky," which spawned five sequels, is the James Bond series. But six actors have played the suave British secret agent. Try to imagine any of the later treatments of the so-called "Italian Stallion" with someone other than Sly in the lead role. Can't be done, right?

Stallone also hit a home run, but maybe not a grand slam, with the four-flick "Rambo" series, but, taken on balance, his celluloid career probably includes more misses than hits. He has made some astoundingly bad choices in the selection of roles that might have established him as something other than a two-trick pony, but whenever the box-office take and critical acclaim began to dry up, there were always those old reliables to fall back on.

"I'll just go on making 'Rambo' and 'Rocky,' " Stallone, now 64, said a few years ago, during one of his periodic lulls. "Both are money-making machines that can't be switched off."

But as profitable as the John Rambo character was for Stallone, his heart - and the world's - is more readily given to the guy who fell in love with the pretty but shy Adrian, who made ends meet by serving as a kindhearted enforcer for a loan shark, who was always loyal to his crusty trainer, Mickey, and unaccountably so to his schlub of a brother-in-law, Paulie. Change any of the elements of the original story - which Stallone wrote in only 3 days after being inspired by Chuck Wepner's failed challenge of heavyweight champion Muhammad Ali - and maybe some or all of the Rocky magic disappears.

Even Sly himself sometimes is at a loss to explain why Rocky became as integral and enduring a part of a public consciousness as any movie character ever has. Upon being told in December 2005 that the Boxing Writers Association of America had selected him to receive a award for "lifetime cinematic achievement in boxing," Stallone said he could not have anticipated Rocky's ability to keep going the distance.

"People accept Rocky Balboa as authentic," said Stallone, who was putting the finishing touches on 2006's "Rocky Balboa" when told of that honor. "I can't tell you how many people have come up to me and asked about my boxing career. It's like they really want to believe that Rocky exists.

"You know, I'm amazed by all of this. At one time, I thought people would get over [their fascination with the character] and move on. Didn't happen. After 30 years, Rocky has taken hold to a degree I never could have imagined."

It's still taking hold. A statue of Balboa, a prop from 1982's "Rocky III," might have been viewed with disdain by certain board members of the Philadelphia Museum of Art, whose steps Rocky so famously climbed, to the strains of "Gonna Fly Now."

But so many locals and visitors clamored for it to be put on display there that it was permanently relocated from the about-to-be-demolished Spectrum to a place near the base of those steps in 2006. It is now, and probably always will be, one of Philly's top tourist attractions.

Stallone also is collaborating with Tony Award-winner Thomas Meehan, who wrote the librettos for "Annie" and "Hairspray," on "Rocky: The Musical." Plans call for the play to be first performed in Germany in the fall of 2012 before debuting on Broadway in the spring of 2013.

What could possibly top all that? Well, maybe a biographical movie about an even longer longshot than Rocky, namely Stallone himself.

Born Michael Sylvester Gardenzio Stallone in the gritty Hell's Kitchen section of New York to an Italian hairdresser father and an astrology-obsessed mother, the future Rocky was expelled from 14 schools before age 13 for antisocial and violent behavior. At 15, his classmates voted him the one "most likely to end up in the electric chair." Much of Sly's defiant ways were acted out in Philadelphia, where the family moved in the early 1960s, or its surrounding areas; he never completed the 10th grade at Lincoln High before enrolling in Devereux Manor High in Berwyn, Chester County, a school for emotionally troubled youths.

Stallone was homeless and sleeping most nights in New York's Port Authority bus terminal when he accepted $200 for his first starring role, a soft-porn movie called "The Party at Kitty and Stud's," which was released in 1970. He appeared naked in nearly all of his scenes.

Having determined that writing his own scripts might boost his flagging acting career, Stallone wrote the screenplay and co-starred in 1974's "The Lords of Flatbush," whose cast included a pre-Fonzie Henry Winkler, in which he portrayed a leather-jacketed '50s tough guy. But, a year or so later, it's said he had only $106 in his bank account when United Artists executives - who reportedly envisioned Ryan O'Neal in the lead role - green-lighted "Rocky," with no expectations that it would be anything close to the international smash that it became.

So impressed by Stallone's star-making turn (Sly was nominated for Best Actor and Best Screenplay Oscars) noted Chicago Sun-Times film critic Roger Ebert predicted he could become "the next Marlon Brando."

What has followed has been . . . well, no one compares Stallone to Brando anymore. One warts-and-all bio of Stallone reports that he passed on the lead role in 1978's "Coming Home" that went to Jon Voight, who won the Academy Award for Best Actor. He also declined the role accepted by Christopher Reeve in 1978's "Superman," as well as the ones that went to Harrison Ford in 1984's "Witness," to Eddie Murphy in 1984's "Beverly Hills Cop," to Bruce Willis in 1988's "Die Hard" and to Dudley Moore in 1992's "Arthur." But he signed on to such ill-fated projects as 1984's "Rhinestone" and 1992's "Stop! Or My Mom Will Shoot."

That kind of decision-making played no small part in Sly being nominated a record 30 times for the Golden Raspberry Awards, usually in the "Worst Actor" category, which he's won 10 times. The Golden Raspberry Foundation named him "Worst Actor of the Century" in 2000.

But Stallone could live comfortably off the megamillions he's already banked from the "Rocky" and "Rambo" series, with large checks continuing to come in from residuals, the gift that keeps on giving. One of his more recent action flicks, 2010's "The Expendables," grossed $266 million worldwide.

And as of tomorrow, he joins the company of Sugar Ray Robinson, Joe Louis, Muhammad Ali, Joe Frazier and any number of boxing legends whose fights were not choreographed.

Yo, Adrian, he did it. *