The Princess Bride's Cary Elwes Says He 'Hit the Jackpot' with the '80s Cult Classic: 'It's Inconceivable' (Exclusive)

Cary Elwes knows he got lucky with his iconic Princess Bride role!

At the premiere of his upcoming Paramount+ series Knuckles, a spin-off of the Sonic the Hedgehog movie franchise, Elwes describes the 1987 fantasy film to PEOPLE as “the gift that keeps on giving.”

The 61-year-old actor — who starred as farm boy-turned-pirate Westley in the film, now a cult classic in the fantasy genre — also credits the Rob Reiner-directed flick for solidifying his comedy chops.

When asked whether he felt he had to prove he could do comedy early in his career, Elwes tells PEOPLE, “Well, Rob Reiner really helped me with that.”

“Once I got that part, that really kind of opened the door for me and that's how I got the role of Robin Hood with Mel Brooks,” he said, referring to his titular role in 1993’s Robin Hood: Men in Tights.

"So that was really Rob basically saying, ‘I believe that you can do comedy and I can believe you do serious as well.’ So, yeah,” Elwes added.

Discussing his relationship to the film — which also starred Robin Wright, Mandy Patinkin, Billy Crystal and Andre the Giant — Elwes says it is still integral to his career today.

“I have sold-out shows,” he tells PEOPLE. “I tour with the movie and I sell out everywhere I go. It's crazy. It's really beautiful.”

And, nodding to Wallace Shawn’s most iconic line from the film, the actor adds that the enduring success he experiences from Princess Bride is “really inconceivable, to use a word that's famous from the movie.”

"You're lucky as an actor to have anyone resonate with your work,” he says, “and I seem to hit the jackpot with that one.”

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Elwes — who, after The Princess Bride, went on to star in not only Robin Hood but also the first Saw film — recently opened up to PEOPLE about a different project: his latest movie, The Ministry of Ungentlemanly Warfare.

The star revealed that he has a special connection with the character he portrays in the World War II thriller — Brigadier "M" Gubbins, the man personally chosen by British Prime Minister Winston Churchill to run the Special Operations Executive.

"My grandfather was actually recruited by the character I play in the film," he revealed to PEOPLE. "He was dropped into Albania in 1943 to create a partisan brigade to fight the Italians and the Germans."

Added Elwes: "He would regale me with stories when I was a kid, and he was my real-life hero. So this is a deeply personal project for me."