On a blustery February evening in Midtown Manhattan, opposite an unmarked side entrance to the Ed Sullivan Theater, a crowd of more than 60 people stood crushed against a row of steel barricades. They all knew that at any moment, Harrison Ford would arrive for an appearance on “The Late Show With Stephen Colbert.” They elbowed and cursed one another, jockeying for position, each clutching a sheaf of photographs for Mr. Ford to sign.They weren’t fans — not most of them, anyway. They were “graphers,” who make a living by hounding celebrities for autographs and selling them to the highest bidder. For many of them, graphing is a full-time job. Some have been at it for decades. They can flip a single signature for anywhere from $25 to more than $1,000, depending on a star’s cachet and how frequently they sign. A Harrison Ford autograph, for example, retails for about $750.At 5:30 on the dot, a black Escalade pulled to a stop in front of the theater. The rear door swung open, and the pack of graphers across the street broke into a frenzy. “Harrison!” they hollered. “Harrison, please!”Slumped near a dumpster by the stage door, a disheveled man with a mane of gray hair and a wild beard let out a grunt. He clambered to his feet, reached into a grocery bag and pulled out an overstuffed FedEx mailer, inscribed in large, looping cursive with a note. “Thank you, Harrison,” it read. “Love, Radio Man.” He staggered past the theater’s security team and approached the Escalade.“Harrison!” the man called as Mr. Ford climbed out of the back seat. “How are ya?”Mr. Ford grinned. “Radio,” he said warmly. They shook hands. Fifty feet away, the graphers behind the barricades bellowed in a desperate chorus.Giovanni Arnold, who has been graphing in New York City since 1999, unrolling movie posters outside the Edison Ballroom. He waited outside for over three hours hoping to get Mr. Spielberg’s autograph as he entered the venue for the Writers Guild Awards.Jonah Rosenberg for The New York Times“Listen, I’ve got some photos for you,” the man said, handing Mr. Ford the package.“Sure, sure,” Mr. Ford said, accepting it. They made small talk. Mr. Ford asked after the man’s health, and the man asked after Helen Mirren, Mr. Ford’s co-star on the “Yellowstone” spinoff “1923.”“Good to see you, Radio,” Mr. Ford said. He slipped into the theater without acknowledging the graphers screaming his name. They would have to wait until he had finished his interview.There are at least 150 professional graphers in New York City, according to Justin Steffman, the founder of the autograph authentication company AutographCOA. And right now, they are working at full tilt. All winter long, celebrities have been flocking to New York to campaign for projects up for various film and television awards, culminating in the Oscars. For graphers, collecting signatures during awards season is like fishing at a trout farm.The rest of the year is by no means slow. Stars are always cycling in and out of Broadway theaters, concert venues, luxe hotels, film shoots and, most reliably, morning shows like “The View” and late-night shows like Mr. Colbert’s. Their constant presence has made New York the graphing capital of the United States, topping even Los Angeles, whose sprawl, closed sets and tight security make life more challenging for graphers. “It’s got to be a billion-dollar industry,” Mr. Steffman said. “It’s gotten bigger and bigger and bigger.”There are at least 500 full-time graphers around the world, Mr. Steffman said, and thousands more who graph on a regular basis.But none of them do it quite like Radio Man.Radio Man — legally known as Craig Castaldo, though no one ever calls him that — has been graphing in New York since the early 1990s. Over the years, he has managed to charm a small army of celebrities into accepting his hefty packages of photographs, which they sign and return to him. Where most graphers would be lucky to get more than one signature from a star at a time, Radio Man regularly nabs dozens, sometimes hundreds. He considers the A-listers who sign for him his personal friends.Craig Castaldo, known to all as Radio Man, outside the Ed Sullivan Theater in New York during a taping of “The Late Show With Stephen Colbert.”Jonah Rosenberg for The New York TimesAfter his exchange with Mr. Ford, Radio Man made his way to the Park Hyatt to pick up a package that Sarah Michelle Gellar had left for him at reception. It was adorned with a heart in black Sharpie, along with a handwritten note: “Only for you, Radio.” Inside were 43 signed photographs of Ms. Gellar.“It’s amazing how they take to me, these actors,” Radio Man said. “A bum! I don’t understand it.”Radio Man, 72, lives just above the poverty line, in a basement apartment in Yonkers he rents for $900 a month. He commutes into the city each morning on his bicycle, a 13-mile journey that takes him about two hours. He said he survives exclusively on food he gathers from free pantries and movie sets.Though he could make a small fortune selling his autographs directly to collectors, his grasp of the necessary tools — photo databases, printers, the internet — is tenuous at best. Instead, like most graphers, he peddles his merchandise to a dealer, who in turn hawks it at a significant markup on eBay and other, more obscure autograph marketplaces.Leaning against a wall outside the Park Hyatt, Radio Man pulled out his phone and made a call. A few minutes later, a silver sedan pulled up to the hotel. A tall, middle-aged man with close-cropped hair and a manicured beard stepped out of the car and into the frigid night. Radio Man handed him the package of signed photographs from Ms. Gellar, and the man accepted them without a word. He hurried back to the warmth of his car, leaving Radio Man alone next to his bicycle.“Hey,” Radio Man called out to him. “You got six bucks so I could get a tea or something?”“I don’t have any cash on me,” the man said. He ducked into the car and drove away.The man, Radio Man’s de facto handler, supplies him with his FedEx mailers of photographs. Once Radio Man gets them signed, the handler sends them to a dealer based in Florida, who is rumored among graphers to be a millionaire. All told, the autographs Radio Man received from Ms. Gellar are worth approximately $6,000. He was paid about $300 for them.“Let them make all the money they want,” Radio Man said. “I don’t care. As long as I get to see my friends.”By “friends,” he meant the celebrities who have taken an unlikely shine to him since he stumbled into their world more than 30 years ago.As Radio Man tells it, he made his first famous friend when he was homeless. One winter day in 1990, he was walking through Central Park when he encountered a man dressed in rags, whom he took for “a bum like me,” he said. He offered the man a beer. “Do you know who I am?” the man asked.It was Robin Williams. He was shooting “The Fisher King,” Terry Gilliam’s 1991 film in which Mr. Williams plays a vagabond searching for the Holy Grail.The actress Riley Keough signed autographs from her S.U.V. after a taping of “The Late Show.” Graphers chased her car down the street, catching up to her at a red light.Jonah Rosenberg for The New York Times“You’re doing this all wrong,” Radio Man told him. “You’re not acting the way a bum should be.”He introduced the actor to life on the street, showing him “where to go and what to do.” Mr. Williams patterned his performance in “The Fisher King,” which earned him an Oscar nomination, after Radio Man. Or so Radio Man claims.In exchange for his guidance, the movie’s producers gave Radio Man $200 and a case of beer. They also cast him as an extra. From then on, he made a habit of hanging around film sets in New York, where he helped himself to food from craft-services stations and scored low-paying parts as a background actor. Graphing was an easy way to make money.“I’ve been getting movies ever since,” Radio Man said. “Here and there, playing my role: bum, homeless guy, guy on a bicycle with a radio.”But that’s just one version of the story Radio Man tells about his origins.Another version involves running a newspaper stand in the 1970s and being cast as an extra in “The In-Laws,” starring Peter Falk and Alan Arkin. Another involves sharing a beer with Bruce Willis on the set of “The Bonfire of the Vanities.” Yet another involves showing up to shoots with a boombox around his neck and playing it at full volume until someone paid him to leave, a racket that supposedly earned him his nickname. (“A cop was there and he said to me: ‘Hey, radio guy! Hey, radio person! Hey, radio man! Can you turn that down, please?’ And that’s how I became Radio Man.”)Whatever he may claim about his past, this much is true: Radio Man is a fixture on film sets in New York. He has appeared as an extra in dozens of movies, including “Ransom,” “Zoolander,” “The Departed” and “The Irishman.” He has a preternatural knowledge of actors’ whereabouts and shooting schedules. And he has forged something like a friendship with some of the biggest names in Hollywood.Radio Man biking through Midtown Manhattan after staking out the stage door to “The Late Show.” He was hoping to see Sarah Jessica Parker at a nearby filming location.Jonah Rosenberg for The New York TimesOn a January night in Chinatown, Radio Man sauntered around the set of “Wolves,” a forthcoming movie starring George Clooney and Brad Pitt, as if he were its executive producer. He weaved through packs of stagehands, chatting amiably with anyone who crossed his path. During a break in shooting, he shuffled over to Mr. Clooney, who was sitting in a director’s chair. “Clooney!” he shouted, followed by an expletive-laden insult.“There it is,” Mr. Clooney said.“You know where you’re going tomorrow?”“I don’t know where I’m going tomorrow,” Mr. Clooney said.“Under the Manhattan Bridge.”“See, this is what I’m talking about,” Mr. Clooney said, as the production crew standing around him laughed. “You don’t need a call sheet. Radio Man is the call sheet.”Mr. Clooney first met Radio Man in 1996, on the set of “One Fine Day” in Manhattan. The actor has “never not seen him” during a trip to New York since, he said.“Radio’s everywhere,” Mr. Clooney said. “Every hotel you show up at, Radio will be standing out in front of it going, ‘De Niro’s over at this, and Cate Blanchett’s over here staying at the Carlyle.’ He’s got all the intel.”Radio Man endeared himself to Mr. Clooney, the actor said, after rescuing his wife, Amal Clooney, from a throng of paparazzi that had swarmed her on Fifth Avenue. Radio Man blocked them with his bicycle, hailed a cab and steered Ms. Clooney inside, securing her escape.“He’s a great guy,” Mr. Clooney said. “He’s a lovable mess, which we all are.”About six years ago, Mr. Clooney got together with a few other actors and flew Radio Man out to L.A. They sent him to the Oscars. He wore a tuxedo. He walked the red carpet. He sat in the audience. He brought a date.A grapher outside the Ed Sullivan Theater with the tools of the trade. She was among a small crowd hoping to get signatures from Michelle Yeoh and Riley Keough.Jonah Rosenberg for The New York TimesA few nights after bumping into Radio Man in Chinatown, Mr. Clooney poked his head out of a white trailer parked on East Broadway and peered down the street. “Radio!” he yelled.Radio Man ambled over. Mr. Clooney strode toward him holding a large bag, trailed by a pack of photographers.“Here you go, Radio,” he said, dropping the bag on the sidewalk with a thunk. “This thing weighs a ton, by the way.”Radio Man reached inside and pulled out two bulging FedEx mailers. They contained 185 signed photographs of Mr. Clooney, worth approximately $18,000.Mr. Clooney said that Radio Man is the only grapher he will take a package from. But he signs for all of them.“Every one of these guys who come over for autographs, it’s a business for them,” he said. “You try to help them out when you can.”“My job baffles me,” said Mr. Arnold. “Personally, I wouldn’t buy an autograph. It would be of more sentimental value if I got the autograph myself, but if someone else got it, it’s just weird.”Jonah Rosenberg for The New York TimesThere is at least one other grapher in New York capable of exchanging packages with celebrities: Giovanni Arnold, 38, who has been graphing in the city since 1999. He calls himself “Black Radio Man.”“There isn’t really an elite group of graphers who are getting packages,” Mr. Steffman said. “There’s Gio, and there’s Radio Man.”On a Saturday afternoon in January, Mr. Arnold sat in a dark bar in the East Village indexing several large bags of autographed memorabilia he had just received from Daniel Radcliffe, who was starring in a production of “Merrily We Roll Along” at the New York Theater Workshop a few blocks away.He laid out his haul on a grimy, beer-stained table, examining each item — cheaply printed photos, plastic Harry Potter eyeglasses, Gryffindor neckties — for Mr. Radcliffe’s signature. He counted 95 autographs in all, whose total value he pegged at $10,000. “I’m hype right now,” he said. “He really blessed me.”Mr. Arnold celebrated with a Guinness. He took a sip from his pint glass and shook his head, pondering a question that has long puzzled him: Why would anyone pay for an autograph?“My job baffles me,” he said. “Personally, I wouldn’t buy an autograph. It would be of more sentimental value if I got the autograph myself, but if someone else got it, it’s just weird.”Mr. Arnold has taken a different approach to the business of graphing than most of his peers. He sells his own merchandise on eBay, as well as directly to private collectors, which has allowed him to accrue a level of wealth few graphers seem to enjoy.He documents his day-to-day life hunting for autographs on Instagram under the handle @gtvreality, where you might find him giving Lady Gaga a ride on his bicycle, holding hands with Ben Affleck or shouting his catchphrase — “Stay Black!” — at Bob Dylan. He hopes to turn GTV Reality into a full-fledged brand and to monetize his content, though at 5,000 followers, he hasn’t quite figured out how to do so.“I’m trying to move in a different direction,” he said. “Everyone and their mama’s an autograph-getter now.”Ultimately, Mr. Arnold wants to find a way out of the memorabilia industry. He doesn’t derive the same kind of joy that Radio Man does from chasing down celebrities, and he isn’t willing to dedicate his life to it.“I’m good at what I do,” Mr. Arnold said. “But he’s another level.”“Let them make all the money they want,” Radio Man said of the autograph middlemen. “I don’t care. As long as I get to see my friends.”Jonah Rosenberg for The New York TimesBack on the set of “Wolves,” Radio Man cruised the streets of Chinatown looking for the director, Jon Watts. He was hoping there might be a scene he could sneak into. But the cameras were already rolling, and Mr. Watts was occupied.Radio Man returned to his usual post outside Mr. Clooney’s trailer. It was closing in on midnight. He was standing near his bicycle and sipping a hot tea, killing time until the next break in filming, when he was approached by someone he didn’t recognize.“Radio,” the man said. He held up an 8-by-10-inch photograph, taped to a sheet of hardboard, of Radio Man. “Do you mind signing real quick?”“What do you want me to say?” Radio Man asked. “Just, Radio Man?”“Yeah,” the man said. “Radio Man.”Radio Man signed the photograph in big, sloppy cursive. The man thanked him and walked away. It was hard to say if he was a grapher or just a fan. More