Bart Simpson’s “dude” may be one of the most instantly recognisable refrains in television history, so imagine hearing it step out of the screen and into real life.

That was the case for 13-year-old American high school student, James, when he unwittingly sold charity chocolate bars to Nancy Cartwright, the actor who has voiced the 10-year-old skater kid for 30 years.

In a video shared by Cartwright’s own production company on Twitter, the seasoned voice actress approaches the teenager to ask him about his fundraising efforts.

But halfway through the conversation she switches into Bart Simpson mode, leaving the stunned eighth-grader speechless.

“That’s a really good impression,” he says.

“Is it pretty good? Do you know the guy that does it?” Cartwright asks.

“I don’t,” the clearly oblivious student responds, before Cartwright unleashes the full power of her vocal skills.

“Well shake my hand,” Cartwright says, as her unwitting target comes to realise who he’s speaking to.

“What’s happening man, high-five dude!”

Our very own @nancycartwright charming the world as Bart from @TheSimpsons This is adorable! His face when he realizes is priceless! pic.twitter.com/CpPgvV2hCL

— CRE84U Entertainment (@CRE84UEnt) March 24, 2017

Not only did James get to meet a television legend, he also managed to offload plenty of fundraising chocolate bars too.

Cartwright, 59, clearly enjoyed the impromptu prank.

“I don’t know who was more excited, him or me, I swear,” she told the camera. “I am so lucky. I am so, so lucky.”

The video soon gained traction online and Cartwright shared her delight, tweeting: “Awe, James and I went ‘viral’ on Facebook! Having such fun reading all of your comments! Thanks for all the support guys! Cowabunga!”

Cartwright scored the coveted role of Bart Simpson in 1987, when she auditioned for the show – then just a skit on The Tracey Ullman Show  – and was such a natural that creator Matt Groening hired her on the spot.

Today, after 28 seasons of the animated series, Cartwright has an estimated net worth of $US70 million ($A91.6 million).