“People kept telling me I was a dead ringer for that guy from 21 Jump Street,” says Ronnie Rodriguez, a California-based Johnny Depp and Captain Jack Sparrow impersonator. “I didn’t really think much of it until the first Pirates of the Caribbean movie came out.”

Eventually, they all give in to the inevitable. Rodriguez, for instance, dressed up as Jack Sparrow for a Halloween party, where a friend insisted Rodriguez send a picture to an agency in L.A. Two weeks later, he was working on a Japanese TV show.

“They put me up in a nice hotel in Beverly Hills, paid me really well, stuck me in front of a camera beside a couple of Tom Cruise and Steven Spielberg look-alikes, and I thought, ‘Boy, a guy could get used to this sort of thing,’ ” he says.

Now, Rodriguez, who won the 2008 Rising Star Reel Award, logs between 10 and 15 Depp gigs in a good month. They range from bits in spoof movies to headlining at a Toyota sales-manager meeting to handing over a set of car keys to a birthday girl at her sweet-16 party to the ultimate A-list assignment, a nine-month stint working as Depp’s photo double on the set of Pirates of the Caribbean: At World’s End.

“Very few impersonators get to actually work alongside the person they impersonate,” Rodriguez says. “I’m one of the lucky ones.”

Joe Manuella, a veteran Robert De Niro impersonator, is one of the few others who has rubbed shoulders with his inspiration. The retired firefighter, who was born in Brooklyn, performs regularly at events throughout the Northeast and has worked as a double for De Niro in three films.

“I was on set one time,” Manuella recalls, “and I heard some guy behind me yell, ‘Hey!’ So I turned around, and there was Robert De Niro staring at me. He flashed that grin of his and said, ‘You look familiar.’ I thought that was a pretty nice compliment.”

Three years ago, Sharon M. Holmes innocently logged on to Martha Stewart’s website in search of a chocolate-pecan-pie recipe. Holmes never found a recipe, but she instead stumbled across a quirky online casting call for The Martha Stewart Show. “Has anyone ever said you look like [Martha]?” it read. “Send us your photo.” For kicks, the businesswoman, who was based in Orange County, California, and regularly got mistaken for Stewart, sent in half a dozen shots of herself and waited anxiously. When she didn’t hear from anyone at the show for two months, she assumed they weren’t interested in her.

One month later, she got a call. Among thousands of prospective look-alikes who’d sent in their photos, Holmes had been selected as the closest match. She was flown to the studio in New York City, met Stewart in front of the cameras, and started getting calls about it.

“I was ready for a career change, and there was this whole chain of events that made it almost feel predestined,” says Holmes, who began taking a year’s worth of acting classes and public-speaking seminars to perfect her impersonation craft. Her business card now features a photo of her and Martha together. “The idea that I could make a living doing what comes naturally — looking like Martha — just felt like this wild and incredibly fun opportunity.”

Greg Thompson’s foray into the world of impersonation was similarly unpremeditated. Ten years ago, the Florida-based entertainer was hired to produce a large event at Universal Studios. He recalls, “We needed 35 actors, including an Austin Powers impersonator, who we still didn’t have five days before the show. We literally had an Austin Powers emergency on our hands.”

That’s when Thompson bought himself some novelty teeth, a brown wig, and a blue-and-silver-striped suit. He adopted an English accent, and a bankable alter ego was born. Today, Thompson’s Austin Powers work makes up a good chunk of his income — along with the annual Sunburst Convention of Celebrity Tribute Artists, which he founded with his wife, Jackie. For impersonators, it’s considered a must-attend gathering, where they can connect with peers, hobnob with talent buyers, and hone their craft.

“We teach celebrity tribute artists about everything from marketing themselves to costume care to proper etiquette,” says Thompson. One of the issues Thompson helps impersonators tackle is choosing the right subject.

“Sometimes, we get people showing up saying, ‘I’m Endora from Bewitched,’ ” he says. “But is there any call for that? This isn’t a costume contest. It’s not Halloween. It’s not a joke. It’s a real business, and it takes serious work, training, and real talent to be good.”

And if you are good? “You can make a six-figure income,” he says.

“It’s a fabulous business,” says Monroe impersonator Griffiths. “Sure, there can be this incredibly cheesy element to it, but at its best, it’s also a unique art form — and probably an underappreciated one. After all the gigs I’ve done, I’m still so touched when some guy at a casino tells me, ‘You know, when you get up there, it’s like Marilyn Monroe just entered the building.’ ”

Turner impressionist Vest agrees that the validation is what makes her job so rewarding, especially when it comes from Miss Proud Mary herself.

“I was doing my Tina show [at a resort in South Africa], and she was there preparing for her Wildest Dreams tour,” recalls Vest, who went to watch her muse rehearse several times. “Everyone in the band had seen my show except for her. One of them pointed to me, turned to Tina, and said, ‘That’s Hollie. That’s the girl who does you.’ ”

From the stage, Turner looked Vest dead in the eye, blew her a kiss, and gave her some sound career advice: “If you’re going to do it, do it from the heart.”