One of the best movies of the 90s,

Good Will Hunting

's perceived overnight success was anything but.

The 1997 flick actually took years to reach the screen but went on to win three Academy Awards and gross more than $220 million.

Celebrating its 20th anniversary this year, the movie was also instrumental in catapulting the young Matt Damon and Ben Affleck to Hollywood juggernauts.

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From hiding secret sex scenes in their script to scoring houses with simple magazine quotes, here's everything you might not know about the cult classic that had all of us wishing we were mathematical prodigies.

Spielberg was annoyed the movie was so successful

While Saving Private Ryan will always be one of the greatest war dramas of all time, the film's director Steven Spielberg didn't choose Matt Damon for his acting chops.

Spielberg told Roger Ebert back in 1998 his main reason for casting Damon in the blockbuster war film was because no-one knew who he was. He wanted someone with an 'All-American look' and Damon had that.

Actor Matt Damon and actor Ben Affleck attend the 70th Annual Academy Awards. Photo / Getty
Actor Matt Damon and actor Ben Affleck attend the 70th Annual Academy Awards. Photo / Getty

He probably didn't anticipate how well

Good Will Hunting

was going to do or that Damon would be a huge star before

Saving Private Ryan

was released.

Spielberg admitted, "Who knew he was gonna go off and become a movie star overnight and win the Academy Award for screenplay? And not be the anonymous actor I had in mind?"

How Damon and Affleck made sure people were reading their script

It shouldn't come as much of a shock that most of Hollywood's big studios tend to scan rather than properly read potential scripts.

Damon and Affleck knew this and developed a sneaky trick to make sure people were actually reading.

The pair decided to write full sex scenes between the characters Sean (played by Robin Williams) and Will (played by Matt Damon) deep in the script but, despite the erotic additions, no one made mention of them.

It wasn't until Harvey Weinstein of Miramax got his hands on the script that the boys heard some constructive criticism.

Weinstein would love to produce the film, as long as they agreed to take out the sex scene.

Damon and Affleck knew he'd read the script and chose Miramax to produce the film.

Boston wasn't the safest place at the time

One of America's most notorious mobsters Whitey Bulger was still running South Boston back in 1997 and the area was crawling with ruthless Irish gangs.

Despite that, Robin Williams insisted on checking out the 'Southie' neighbourhood to get a feel for the area, a decision that Affleck remembers as "a f**king mistake."

After heading to the L Street Tavern, the bar they would eventually shoot in, Affleck was almost bashed for wearing his hat backwards and Williams was mobbed by Irish guys asking "where his private plane was."

After their close mobbing, Weinstein sent a furious message to the two writers saying 'DON'T TAKE ROBIN TO ANY MORE LOCATIONS.'

A magazine quote scored Damon and Affleck a house

The writing duo were still in their 20s when the script was picked up and like most mid-20 year olds, their credit rating wasn't the best.

Thanks to an article in the Daily Variety however, that no longer mattered.

Matt Damon and Ben Affleck at the premiere of Good Will Hunting. Photo / Getty
Matt Damon and Ben Affleck at the premiere of Good Will Hunting. Photo / Getty

The magazine printed the boys would get a cool $675,000 for their script, which they used as a rental application.

"We had no credit, so we went to rent this house that was $3,000 a month, and we used a copy of the Daily Variety to get the place. I was like, "I don't have credit, but this is who we are." And the landlord was like, "All right, sure," Affleck recalls to Boston Magazine.

The script money might've secured them a house but it didn't last as long as they expected.

"We thought $600,000 would take care of us for 20 years, so we rented nicer apartments and each bought Jeep Cherokees. And we were completely broke in a year," Affleck added.

The movie is full of references to their real lives

Damon and Affleck weren't afraid of using their own lives as inspiration for Good Will Hunting.

Minnie Driver's character Skylar was based on Matt Damon's girlfriend Skylar Satenstein who was also a medical student at Harvard.

Actor Matt Damon and ex girlfriend Skylar Satenstein. Photo / Getty
Actor Matt Damon and ex girlfriend Skylar Satenstein. Photo / Getty

They didn't get their movie happy ending though - Satenstein left Damon before filming for Lars Ulrich, the drummer of Metallica.

The phone number listed for the construction company the boys worked at was also the actual number for a Massachusetts construction company Damon worked for in high school.

Sean and Will briefly discuss the painting hung in the therapist's office which Will calls "a piece of s**t" and Sean admits is actually a "paint by numbers" artwork.

Matt Damon, Minnie Driver, and Ben Affleck during AFI Benefit Premiere of Good Will Hunting. Photo / Getty
Matt Damon, Minnie Driver, and Ben Affleck during AFI Benefit Premiere of Good Will Hunting. Photo / Getty

The painting was actually done by the movie's director Gus Van Sant, who must've signed up his artwork to cop the critique.

The scene that made Damon and Affleck cry

After years of development and back and forth between production companies, it was almost a miracle when Good Will Hunting started shooting.

The first day of filming included a scene between Robin Williams and Stellan Skaarsgard which was an emotional one for the young writing duo.

"We watched these guys - I mean accomplished actors - do our scene verbatim, we had waited so long for this to happen. I remember just sitting next to Ben and I had tears rolling down my cheeks because I was just so happy and relieved that it was really happening," Damon told the Boston Magazine.