When an arrogant, aging, iconic comedian of yesteryear met an overly confident, young, up-and-coming comedian just making his mark on the industry, it was pretty much a given that their worlds would collide. And in Jason Reitman’s “Saturday Night” — a “based on a true story” account of what happened 90 minutes before “Saturday Night Live” debuted in 1975 — that’s exactly what happened between Milton Berle and Chevy Chase when they met. It wasn’t so much a passing of the baton as it was a “Mine is bigger than yours.”

JK Simmons plays Berle, a superstar of his era as a funny man on radio and television who eventually became known as Mr. Television, opposite Cory Michael Smith’s Chase in the biographical comedy. When Reitman approached Simmons about the role, the Oscar winner said he was intimidated, but was assured that they were not looking for an impressionist to tackle the role, but rather a good actor who could could “understand the guy’s character”.

Although Simmons hadn’t seen the script before taking the job, he knew it would be a supporting role that would appear two or three times, and he was okay with that. And when he finally read the script for the first time, he couldn’t have been happier. “It’s like a snowball rolling downhill and people are either jumping on it or trying to avoid it,” he says, describing the film’s chaotic, kinetic energy from start to finish. And the way in which Berle is interspersed is well thought out. “He, along with the executives at NBC, is everything that all these young, crazy counterculture people want to replace and despise,” Simmons says. “As you know, Berle was a pretty miserable son of a bitch at this point in his life and wasn’t willing to admit that he was on his way out, but he knew it deep down.”

And there’s a particular scene in the film with Smith as Chase that was “a little icing on the cake,” he says. In the scene, Chase catches Berle flirting with Chase’s fiancé (played by Kaia Gerber), and the two men begin throwing sharp comments at each other. Chase gushes about his age to Berle in a “you’re an old man” sort of way, and Berle retorts that Chase is more or less a showbiz nobody and that he has a lot more to give to Chase’s fiancé than Chase does. And then he unzips his pants and pulls out his penis to prove it.

Berle was a notorious womanizer and for many, many decades was considered not the most pleasant person to work with. It was also common knowledge that he was, as they say, “well hung.” It wasn’t just a rumor, as there have been numerous stories over the years – albeit from eyewitnesses – that Berle proudly pulled out his penis and showed it to people. “It was one of those scenes where the ball was put on a tee so Cory and I could take turns knocking it out of the park,” Simmons remembers. “Jason showed us several subtly different and sometimes not so subtly different versions of how to play it.”

The scene is ice cold with a pinch of snark and a dash of bitterness. In it, Berle not only calmly and coolly let off steam, but he also had fun telling this little boy who wanted to replace him that he was messing with the wrong guy. “Whatever respect there may be for each other, there’s no way they’re going to admit it or show it,” Simmons explains. “It’s this pissing competition on different levels. I think Chevy’s disdain for Milton Berle and this world is just typical teenage arrogance. You know: “Nobody was funny until my generation came along.” Berle comes in with his cigar, his coat and his tuxedo, still thinking he’s king of the hill, even though inside he knows he’s slipping. So many comedians have this sad, dark side. And when I researched, I found out what his childhood was like – this poor guy never had a chance to be a decent human being. He wasn’t a happy guy.”

Smith, for his part, had never heard the stories about Berle and his genitals. “I wasn’t familiar with all the rumors and the pride he had in his, um, ‘situation,'” laughs Smith. “But looking back, it’s actually amazing how many stories I was told already Since the film came out, people have reported hearing other stories either first-hand or second-hand. I met a critic who told me the story of standing next to him at the urinal and saying, ‘Don’t wet your pants now.'”

For those watching the film – and yes, you really should – Smith talks about how they played the scene… and the prosthetic mishap that happened during one take. “JK had a complete silicone apparatus, um, on him that he had to, you know, get every shot authentic. It went very well except for one shot where it completely fell out and hit the floor… when the cameras were pointed at my face, by the way.”

A prosthetic penis wasn’t on Simmons’ bingo card and he was actually surprised when it arrived. “I didn’t know about it until I came to Atlanta for a few days (of filming),” he says. “I just assumed the camera would be belt-high and everything else would be left to my imagination. And obviously it isn’t. We’re not going for an X rating, but I didn’t even think it would be a prosthetic. The first time Jason said something like, “You’ve got to get this,” I thought, “Ha!” Simple joke. And then the prop master brought it back in its box like it was a violin, you know, with a velvet-lined case.” He adds with a laugh, “And the rest is history.”

Wait – there’s more. Smith shares: “Jason said there were only two reasons why they used visual effects: one was to change the time on some clocks in the background, because the test audience was very aware of the inaccuracies of the clocks. And the second was to match the color of his prosthetics to his skin color.”