J.K. Simmons is sharing the juicy details about Saturday Night's most memorable prop.

The Whiplash actor recently discussed playing TV legend and funnyman Milton Berle in Jason Reitman's Saturday Night Live biopic — specifically how his character's arc culminates in a scene in which he flashes his notoriously large genitalia to Chevy Chase (Cory Michael Smith) during a tense confrontation backstage.

"I didn't know about it until I got to Atlanta for my few days [shoot]," Simmons said of his prosthetic penis in a new interview with Variety. "I just assumed the camera was going to be belt-high and everything else left to the imagination. And obviously, you know, it's not. We're not looking for an X-rating, but I didn't even think there would be a prosthetic involved."

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In fact, when Reitman mentioned the apparatus, Simmons assumed he was joking. "When Jason first said something about, 'You need to go fit that,' I was like, 'Ha!' Plain joke," Simmons recalled. "And then the prop guy brought it in its box, like it was a violin, you know, velvet-lined case… and the rest is history."

Smith told the outlet about the big snag the stars hit with the fake schlong. "It went very well, except for one take when it fully fell out and slapped the floor," he recalled. "When, by the way, the cameras were on my face,"

Reitman discussed the significance of Berle's flashing scene in a new interview with Entertainment Weekly breaking down the sequence. "The movie is about one generation ripping television out of the hands of the other. How do you personify that?" the director said. "Alright, well, we're going to have a group of young people, and then we're going to have a group of old people. Milton Berle represents everything that television was."

He continued, "He's the ghost of television past. He is vaudeville, he is radio, he is old variety shows, he is sexual harassment, he is all of these things. He will appear later on SNL and do the worst episode of all time. But for us on that night, he represents an idea, yet another barrier that these young people have to cross in order to get the show on air."

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Simmons echoed that idea in his interview with Variety. "Along with the execs at NBC, he's everything that all these young wacky, counterculture people are aiming to replace and are disdainful of," he said of his character. "Berle was, as you know, by this time in his life, a pretty miserable son of a bitch and not ready to admit that he's on the way out, but he knows it deep down."

The actor also said Berle and Chase are emblematic of their respective generations. "Whatever respect there may have actually been for each other, there's no way they’re going to admit or show any of it," Simmons told Variety. "It's that pissing contest on different levels. I think Chevy's disdain for Milton Berle and that world is just typical youthful arrogance. You know, 'Nobody was funny until my generation came along.'"

He continued, "Berle walks in with his cigar and his overcoat and his tuxedo and, you know, still considers himself king of the hill, even though inside he knows he's sliding down. So many comedians have that sad, dark side. And as I researched, I found out what his childhood was like — this poor guy never had a chance to be a decent human being. He was not a happy guy."

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Reitman acknowledged that Berle and Chase probably didn't have this exact interaction in the moments leading up to SNL's first broadcast, but noted that since Berle was notorious for showing off his package, the fabrication was fitting for both of their character arcs. "Chevy is a character who is the personification of ego that must be humbled," the filmmaker told EW. "And we had this great opening line for him: 'Sorry, tripped over my penis.' We thought if we're going to have young and old get into this challenge and have a scene that simultaneously was about the changing of the tides of television, but also about two men getting into a pissing contest about ego, it felt like the perfect construction."

Saturday Night is playing now in theaters.