Judd Apatow can’t be sure anything Mel Brooks told him while making Mel Brooks: The 99 Year Old Man! is true. Early in the two-part doc, Brooks reveals that many of the anecdotes he recounted on talk shows and in comedy routines were exaggerated, or essentially untrue, which also calls into question everything he revealed during the 10 hours Apatow interviewed him.

“The implication seems to be that some of those stories have been punched up,” says Apatow. “We’ll never know exactly what went down. But I don’t think he has been dishonest about his life. As we went along, he got more comfortable, and every once in a while would really surprise us and tell us something that we weren’t even looking for.”

That “us” includes directors Apatow and Michael Bonfiglio, both of whom HBO approached about centering a film on Brooks. What resulted is a three-and-a-half-hour testament to one of the boldest and most influential comedy voices of the past century. Ultimately, Brooks’ past obfuscations gave Apatow and Bonfiglio their hook: How can we peel back the curtain on someone who has kept so much of it drawn?

“We’re making films where we want to introduce you to this person whose work you may or may not know, and then we try to get deeper into understanding these people and what makes them tick,” Bonfiglio says.

During his lifetime, Brooks has channeled the hardships he encountered as a puny Jewish kid and the horrors he witnessed while serving in World War II into fodder for a musical about Hitler (The Producers), a Western satire about racism (Blazing Saddles) and a farce about corporate power (Silent Movie). Even Young Frankenstein and History of the World, Part I possess an admirable thoughtfulness beneath their silly gags.

“There’s a lot of social messaging, but it’s buried way underneath the comedy,” Apatow says of Brooks’ work. “I feel like he finds it distasteful to act like you have some high morality. So if you say, ‘Why did you make fun of Hitler?,’ he’ll say, ‘Because it was funny.’ And he wasn’t just going for laughs — he was going for fall-out-of-your-seat, pee-your-pants laughter.”

The film includes a loving portrait of Brooks’ 40-year marriage to Anne Bancroft, who died in 2005, and a catalog of the many entertainers who have been inspired by him. As Apatow sees it, The Simpsons and Bill Murray’s entire career owe something to Brooks, as do Albert Brooks (no relation), Ben Stiller and every movie based on a zany Saturday Night Live character.

What might be most impressive about Brooks is the way he has maintained what seems like a healthy home life and a contemplative worldview while striving for a certain level of privacy.

“I lead a similar life to Mel in some respects as a person who’s looking at life through a comedic lens and trying to make work that brings joy to people but also has satire and self-exploration and politics involved,” says Apatow. “And also [figuring out], how do you raise a family and be a normal person in this environment of Hollywood and show business and do right by the people in your life?”

This story first appeared in a June stand-alone issue of The Hollywood Reporter magazine. To receive the magazine, click here to subscribe.