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ABC News' Cameron Mathison, Rich McHugh and Lauren Sher:

If you're a child of the 1970 and 80s, you undoubtedly have seen National Lampoon's "Vacation," the 1983 hit comedy about the Griswold family's epic cross-country quest to get to Walley World theme park for vacation.

The flick, starring Chevy Chase, Beverly D'Angelo, Dana Barron, and Anthony Michael Hall, came to define the 1980s in America, spurred countless spoofs and has been dubbed by movie lovers one of the funniest of all time.

" Good Morning America" reunited with the stars of the original cast at Entertainment Weekly magazine's Reunions Issue last month, nearly 30 years after the movie first delighted audiences at the box-office.

One thing was immediately clear: the group still had the same token chemistry as they did when Clark, Ellen, Rusty and Audrey Griswold piled into the Wagon Queen Family Truckster and hit the road on their zany adventure. Shooting the movie was almost as much fun off screen as it was on, the cast said.

"For me it was always laughter and listening going, 'Oh my goodness, did [he] just said that?' … Always a really good time," said Dana Barron, who played the Griswold teenage daughter Audrey. "It was classic, but it was also a family experience for me because we were all on vacation together, literally. So, it became its own film within its film."

While Chevy Chase was the star of "Vacation" as family patriarch Clark Griswold, a young Anthony Michael Hall's career was about to take off. Hall scored a breakout role as son Rusty Griswold.

"He came to life," recalled Beverly D'Angelo, who played the Griswold mom and wife, Ellen. "This was a 14-year-old, and he'd do a take and [you'd] just go, 'Oh my God.' And then he became John Hughes' star. I mean, it was really amazing."

Hall went on to star in Hughes films, including "Sixteen Candles" and "The Breakfast Club," but "Vacation" was his first big break and Hall says it was a real learning opportunity.

"I had no idea [how] to even have a career. This movie gave me a start," Hall said. "I just remembered laughing and having a great, great experience the whole summer."

Much of that comedic atmosphere they credit to director Harold Ramis, who welcomed improvisation on set. Take the hilarious scene where Chase's character dances holding his bologna sandwich to seduce a blond model (Christie Brinkley) dancing outside her red sports car and slaps himself in the face with the sandwich.

"It just came about," Chase said. "She's dancing to some music that's coming out of her car…and I've got the sandwich, and I'm just watching her dance, and I start to dance a little, like Clark would. And I've got this sandwich that I'm eating anyway. At some point I just decided to [flash the bologna]."

Between all the comic asides, there is an unmistakable feeling of family amongst the cast that continues today.

"Chevy's a genius, and my dear friend, and I love you, and I am so glad that the four of us can all be together at the same time to celebrate a special time in everybody's life," D'Angelo gushed.

"What's happened is that generations have watched it now and they've given us back something," she said. "You kind of hope that you can touch somebody's life in some way, and you don't think you're going to do it unless you're getting an Oscar for it. But this movie really - "

"No, I did it for the Greeks and the Chinese," Chase joked.

Watch "Good Morning America" all week as "GMA" and Entertainment Weekly bring together the casts of "Clueless," "Melrose Place" and more.

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For more information on the EW Reunions Issue, visit ew.com/reunions. Fans can bid on memorabilia, meet-and-greets, and more from some of the stars featured in the Reunions issue. Visit charitybuzz.com for more information.