No matter how much Sylvester Stallone has tried, some things in boxing you just can’t make up.

It was enough late Saturday night that a 27-year-old man from Southeast, homeless before a boxing trainer took him and his little brother in when the boy was 10, rocked the fight world by winning his first major world title over the prohibitive favorite.

But when ring announcer Michael Buffer hollered the words, “And . . . NEW SUPER LIGHTWEIGHT CHAMPION OF THE WORLD . . .” and Lamont Peterson smudged his joyful tears against the arms of Barry Hunter and his handlers — and Amir Khan shook his head in disgust after the sport’s umpteenth controversial decision — the night was just beginning for the combatants.

After the postfight news conference, they would bizarrely meet again — in the waiting area of an emergency room.

It was 2 a.m. Sunday outside the George Washington Hospital ER when Peterson’s publicist saw a black Escalade pull up behind his vehicle.

This being the District’s first major championship fight in nearly 20 years, not many medical professionals beyond the ring doctor were present at the Walter E. Washington Convention Center afterward. So Peterson’s people picked the closest facility to their hotel for a genuine postfight examination.

Unknowingly to the new champ, so did the man he took two belts from with a split-decision victory over 12 grueling rounds before an HBO audience.

“I just looked outside and saw all the gold and red from his team and said, ‘Ain’t that some [expletive],’ ” said Andre Johnson, the publicist for Peterson’s camp. “Everybody else in the emergency room just looked at ’em at first, like, ‘What happened to you two?’ ”

Nurses and security officers who had heard about or watched the fight scurried up to the cut and bruised men for autographs. They snapped photographs. Eventually, the two fighters, mutually respectful for almost the entire week leading up to the fight, took pictures with each other before they were treated and released about 5 a.m.

If they had put them in wheelchairs, heck, they would have been Rocky and Apollo at the beginning of “Rocky II.”

Yes, Peterson — the homeless child who dethroned the champion — told Khan he would give him a rematch afterward.

Again, we’re not making this up.

It is going on 5 p.m. Sunday. And as I sit here typing this in the press box of FedEx Field, where the most offensively exciting Washington Redskins game of the year has ended with Tom Brady winning a shootout with Rex Grossman, I can’t get that fight out of my head.

No one can change my mind on this one: The single greatest sports story in Washington this year unfolded past 11 p.m. Saturday night in downtown.

An 8-to-1 underdog, regarded as a very good move-and-stick fighter who competed well but never dazzled on the big stage, knew in the opening rounds he could not outbox a man whose hands moved at warp speed. So he morphed into a free-swinging brawler. His right eye nearly shut, trailing early on the scorecards, Peterson stalked Khan, punishing the champion against the ropes.

Joe Cooper, the Virginia-based ring referee, took two points away from Khan, including one in the 12th round that essentially gave Peterson the decision. Not once did he ever give Khan a bona fide warning custom by most ring referees — something along the lines of, “If you push his head down one more time, I will take a point away.”

The irony was rich because Khan had deigned to come to the contender’s home town for the fight. Now his worst nightmare had emerged: inside job. Perhaps he should have known something was up when Cooper came out in purple surgical gloves, almost perfectly matching the colors of Peterson’s camp.

The deductions took a little away from Peterson’s accomplishment. But the truth: The contender took the fight to the champion, landing devastating shots that went right through Khan’s gloves in many rounds, slamming into his head.

The irascible Larry Merchant had it right when the HBO analyst evocatively declared, “Amir Khan is fighting as if his job depends on it; Lamont Peterson is fighting as if his life depends on it.”

That sentiment was palpable all evening. You could sense it by hearing the corners between rounds. In Khan’s corner, Hall of Fame trainer Freddie Roach dispensed sound strategy, calmly telling Khan: “That’s it, son. Keep ducking under after you throw. Take it to him.”

And in Peterson’s corner, the histrionics of Hunter, the man who saw a child taking care of his brother in the streets almost 20 years ago, was bellowing, “This is it, Lamont! This is all you said you wanted when I met you on the street 17 years ago! This is your moment! Take it from him!”

Lowering his head, throwing right crosses and left hooks with more malice than he ever had before, the child who once didn’t even have a bed to lay his head suddenly was taken in and given refuge — by a city, by a sport, by everyone who knew what a good kid he had always been.

Peterson takes home his greatest payday, $650,000. He will command much more than $1 million for a rematch against Khan. And whatever happens from here on out, he will always have that moment, when Buffer yelled, “And NEW . . .” and everything he dreamed possible happened, right down to Merchant interviewing him in the ring afterward, just like all those great fighters he watched as a kid.

Late Saturday night, when most of Washington was in bed, at a holiday party or up to no good, the local sports story of the year happened.

“It’s about a boxer, that’s not possible,” many will argue.

And as usual, they will miss the point.

It’s not about a boxer. Or this sport, sadly dying every day to find the relevance it once had in an American sports landscape that long ago moved on.

It’s about Lamont Peterson, who happens to box for a living, who fought his way out of abject poverty all the way to the top of his profession.

It’s all unfathomable now, a bit surreal.

Whoever imagined that kid leaving the George Washington Hospital emergency room with a clean bill of health, a smiling 27-year-old at 5 a.m. after having taken pictures with the champion he dethroned, must have had a film script rejected at least once.