Wallace Shawn’s hands would often tremble as he walked onto the set of "The Princess Bride" (1987). It wasn’t the challenge of delivering Vizzini’s complex, fast-paced lines that unsettled him it was the paralyzing fear that, at any moment, director Rob Reiner would decide he was the wrong choice for the role. This fear wasn’t abstract. Shawn was well aware that he hadn’t been the first choice for the character of the self-proclaimed genius Vizzini. Danny DeVito, a towering name in comedy at the time, had been Reiner’s original pick. While scheduling conflicts had taken DeVito out of the running, Shawn felt like an impostor who had lucked into a role meant for someone else.

Shawn’s anxiety wasn’t baseless in his mind. He viewed DeVito as a giant of comedic timing and larger-than-life energy, someone whose every movement commanded attention. Shawn, by contrast, had built his career on intellectual, understated humor in films like "My Dinner with Andre" (1981). He was deeply self-critical, believing his quieter, more cerebral style was entirely unsuited to the flamboyant, arrogant nature of Vizzini. Every take on set was overshadowed by the nagging thought that his performance lacked the boldness the character demanded.

During the filming of the now-legendary "Battle of Wits" scene, Shawn’s insecurities reached their peak. In this pivotal moment, Vizzini engages Westley (played by Cary Elwes) in a duel of logic over poisoned goblets. The scene, layered with rapid dialogue and comedic absurdity, required Shawn to deliver a near-operatic performance, alternating between smug superiority and flustered frustration. While the crew laughed at his pitch-perfect delivery of "Inconceivable!" and his frantic attempts to outsmart Westley, Shawn remained convinced he wasn’t funny enough. He later revealed that he spent much of the scene preoccupied with thoughts of DeVito in his place, imagining the crowd laughing harder and the scene landing better.

What Shawn didn’t realize was how his very fear was shaping his performance in extraordinary ways. Vizzini, after all, is a character who masks deep insecurity with bluster and bravado. Shawn’s real-life unease brought an authenticity to the role that even Reiner hadn’t expected. His voice, with its distinct nasal quality, became an instrument of comedic precision, capturing Vizzini’s arrogance and fragility in equal measure. Every exaggerated hand gesture, every strained attempt at sounding confident, carried a subtle vulnerability that elevated the character beyond mere parody.

Co-stars like Cary Elwes and Mandy Patinkin observed Shawn’s anxiety on set but admired his commitment. Elwes later described how Shawn’s internal struggle mirrored the intensity of the story itself, making his scenes electric. Reiner, meanwhile, never once doubted his casting decision. He saw in Shawn a unique energy that no other actor could replicate. DeVito may have brought a louder, more physical comedy to the role, but Shawn’s version of Vizzini became something more layered a study in the comedy of overcompensation.

Years later, Shawn admitted that his fear of being replaced never fully left him during filming. But it’s this very fear that transformed Vizzini into one of the most iconic characters in "The Princess Bride." The tension between arrogance and self-doubt became the heart of the performance, making Vizzini not just a comedic foil but an unforgettable part of cinematic history.