'Good on Paper' star Ryan Hansen says Iliza Shlesinger coached him on how to play 'sociopath' Dennis, based on someone she actually dated

• "Good on Paper" is a "mostly true" story based on one of Iliza Shlesinger's dating experiences.
• Ryan Hansen told Insider the comedian was "totally coaching" him on how to play Dennis Kelly.
• "She could be like, 'No, no, Dennis would definitely never do that,'" he said.

Warning: This article contains spoilers about Netflix's "Good on Paper."

Before "Good on Paper" opens on one of Iliza Shlesinger's stand-up sets, the Netflix rom-com advises viewers that what they're about to watch is a "mostly true story."

In the hour-and-34-minutes that follows, comedian and aspiring actress Andrea Singer (Shlesinger) comes to terms with the fact that her seemingly too-good-to-be-true boyfriend Dennis Kelly (a supposedly Yale-educated financier played by Ryan Hansen) is, in fact, too good to be true.

Yet, the movie never specifies which parts of Andrea's nightmarish relationship are rooted in reality.

But during a recent Zoom call with Insider, Hansen confirmed that Shlesinger wrote the movie based on one of her own firsthand romantic experiences, sticking fairly close to the real-life events while crafting the script.

"It happened to Iliza," he said, adding that the comedian wouldn't disclose her ex's name to Hansen.

"Throughout shooting and stuff, I'd be like, 'Well, did this actually happen? Did this really happen?' And most of it, yeah, really happened," the 39-year-old actor said.

He clarified that "a couple" details in "Good on Paper" are exaggerated to make the story more thrilling but reiterated that "for the most part, it's all true."

Shlesinger used the experience to help Hansen nail his role as Dennis

Because Shlesinger experienced her version of the Andrea-Dennis situation in real life, she served as an invaluable guide for Hansen as he tried to master his character, who he called "a little bit of a sociopath."

"She could be like, 'No, no, Dennis would definitely never do that. Play it this way. No, he doesn't say that, play it this way,' So she was totally coaching me," the actor told Insider.

Hansen added that Kimmy Gatewood, who made her directorial debut on the project, weighed in as well.

"They totally walked the line on that, and I was their puppet," he said.

Shlesinger says roughly 'two-thirds' of the movie is true

Shlesinger, who stars in five Netflix comedy specials, recently told USA Today that the "first two-thirds of the movie are the mostly true parts."

Like her on-screen character, the comedian said she fell for someone after an airplane meet-cute, only to find out that "everything about them was a lie."

And "every single lie" that Dennis tells in the movie - from reciting the wrong home address to fabricating a sentimental story about Baccarat glasses - came directly from Shlesinger's real ex.

"I didn't have to embellish it at all," she told Looper.

Schlesinger did, however, use her imagination when it came to Andrea and Dennis' high-stakes ending, explaining that she landed on the final scene as "vindication" for "anybody who's unjustly been screwed over."

"I hope people will watch this rom-com and be like, 'Yes! That one was for me,' at the end," she said.

Shlesinger has previously spoken about the ordeal on a 2014 episode of "The Joe Rogan Podcast" and Comedy Central's "This Is Not Happening," according to USA Today's Erin Jensen.

"Good on Paper" became available to stream on Netflix on Wednesday.