The scene where Sean and Will are in his office, and Sean starts talking about his dead wife and her farting antics. These lines were ad-libbed by Robin Williams, which is probably why Matt Damon is laughing so hard. If you watch the scene carefully you can notice the camera shaking, probably due to the cameraman laughing as well.
After the 2014 death of Robin Williams, the Boston Public Garden park bench where he and Matt Damon had their conversation scene, became an impromptu memorial site for the actor with people leaving flowers, quotes and various items at the bench. A petition has been passed around to erect a statue in Williams' memory near the bench.
Casey Affleck ad libbed most of his lines. This frustrated Matt Damon, Ben Affleck, and Gus Van Sant during filming - but they later admitted that Casey's improvised lines were much funnier and better than what had been originally written for him.
When Robin Williams won the Oscar for his supporting role, he sent Peer Augustinski, who dubbed his voice in German, a small replica of the Oscar statue with a note saying, "Thank you for making me famous in Germany."
Director Gus Van Sant at one point asked Matt Damon and Ben Affleck to rewrite the script so that Chuckie is killed in a construction accident. Damon and Affleck protested, but reluctantly wrote the scene in. After Van Sant read it, he agreed that it was a terrible idea.
Initially, producer Harvey Weinstein did not want Minnie Driver at all for the role of Skylar, feeling she wasn't cute enough for the part. Because Gus, Matt and Ben wanted her in the movie, Weinstein ultimately relented and Driver went on to be nominated for a Best Supporting Actress Oscar.
Matt Damon, a former Harvard student, originally intended to make the title character a physics prodigy. He discussed his idea with Sheldon L. Glashow, a Nobel laureate in physics and at the time a Harvard professor. Glashow told him that the premise did not ring true to him and suggested that the main character be a math prodigy instead. He referred Damon to his brother-in-law, Daniel Kleitman, a professor of mathematics at MIT who provided advice on the story. Both Glashow and Kleitman are thanked in the credits.
Matt Damon and Ben Affleck found a clever way to choose the right studio for their script: the story goes that on page 60 of the script, they wrote a completely out-of-nowhere sex scene between Will and Chuckie. They took it to every major studio, and nobody even mentioned the scene. When they met with Harvey Weinstein at Miramax, he said, "I only have one really big note on the script. About page 60, the two leads, both straight men, have a sex scene. What the hell is that?" - Damon and Affleck explained that they put that scene specifically in there to show them who actually read the script and who didn't. As Weinstein was the only person who brought it up, Miramax was the studio chosen to produce the film.
When Will (Matt Damon) and Sean (Robin Williams) meet for the first time in Sean's office, Will recommends that Sean read Howard Zinn's "People's History of the United States". As a boy, Matt Damon was Zinn's neighbor and provided the voice for the CD recording of that book.
According to Matt Damon, when the project was set up at Castle Rock Entertainment, all he and Affleck had heard for the casting over them, was "Leo and Brad", referring to Leonardo DiCaprio and Brad Pitt.
The phone number printed on the sign for the construction company that they are working for is the actual phone number of a Woburn, MA construction company that Matt Damon worked for while going to high school in Cambridge.
After Mel Gibson dropped out of directing, Michael Mann expressed interest in directing. However, he wanted to make two major changes: He wanted Will and his friends to be car thieves, and he did not want Matt Damon for the lead role since he was still relatively unknown then. The producers, who wanted Damon, suggested the Mann film some screen tests with Damon and Ben Affleck. After Mann filmed the screen tests, he went back to the producers and said he still did not want Damon in the lead, so the producers and Miramax parted ways with Mann since the film was Damon and Affleck's project from the start.
An earlier draft of the script had Will Hunting being recruited by the government to become a cryptanalyst (based on his mathematical ability). Rob Reiner reportedly reviewed the script and advised Matt Damon and Ben Affleck to eliminate this subplot. However, there is a reference to it in the final script: the scene where Will meets with NSA agents and explains why he doesn't want to work for them.
To date this is the film with the highest US box office gross with Kevin Smith's name attached to it. All his own films that he has written and directed have not grossed more than $35 million at the US box office.
At a WGA seminar in 2003, William Goldman denied the persistent rumor that he was the actual writer of Good Will Hunting: "I would love to say that I wrote it. Here is the truth. In my obit it will say that I wrote it. People don't want to think those two cute guys wrote it. What happened was, they had the script. It was their script. They gave it to Rob [Reiner] to read, and there was a great deal of stuff in the script dealing with the F.B.I. trying to use Matt Damon for spy work because he was so brilliant in math. Rob said, "Get rid of it." They then sent them in to see me for a day - I met with them in New York - and all I said to them was, "Rob's right. Get rid of the F.B.I. stuff. Go with the family, go with Boston, go with all that wonderful stuff." And they did. I think people refuse to admit it because their careers have been so far from writing, and I think it's too bad. I'll tell you who wrote a marvelous script once, Sylvester Stallone. Rocky's a marvelous script. God, read it, it's wonderful. It's just got marvelous stuff. And then he stopped suddenly because it's easier being a movie star and making all that money than going in your pit and writing a script. But I did not write [Good Will Hunting], alas. I would not have written the "It's not your fault" scene. I'm going to assume that 148 percent of the people in this room have seen a therapist. I certainly have, for a long time. Hollywood always has this idea that it's this shrink with only one patient. I mean, that scene with Robin Williams gushing and Matt Damon and they're hugging, "It's not your fault, it's not your fault." I thought, Oh God, Freud is so agonized over this scene. But Hollywood tends to do that with therapists."
The mathematical equations seen in the opening credits are part of a math technique called "Fourier Analysis" which approximates functions by sines and cosines. It's used a lot in physics and engineering.
The script was originally developed by Castle Rock, the production company of Rob Reiner. When they didn't know what to do with it, filmmaker Kevin Smith took the script to Miramax. It became the highest grossing film in Miramax history until Chicago (2002) topped it.
In the scene on the park bench, Robin Williams gives an example of love that Will hasn't experienced as "going to hell and back for it." In his next movie, What Dreams May Come (1998), Williams does just that for his love played by Annabella Sciorra after she commits suicide.
In his first scene, Robin Williams is standing in front of a black board. Behind him are written on the black board in chalk the words "Susser 1969". In 1969, Williams graduated from Redwood High School, Larkspur, and then continued at College of Marin, Kentfield just a few blocks away from the High School. He became acquainted with the Drama Department there at College of Marin and performed in the production "Taming of the Shrew" by William Shakespeare. Robin William's first stage director was the late Harvey Susser. Thus, the black board "code words" seem to say: "Hey, Harvey! See this! Now I'm the teacher!"
While looking over some of Will's work, Lambeau remarks, "I see you used Maclaurin here," referring to a mathematical representation called the Maclaurin series. Coincidentally, McLaurin was Robin Williams' middle name.
The very first day of the shooting, Matt Damon and Ben Affleck started crying out of happiness, because it was a scene between Robin Williams and Stellan Skarsgård, accomplished actors, doing Damon's and Affleck's scene verbatim and they had waited so long (four years) for this to happen.
When Matt Damon was in his fifth year at Harvard, there was this playwriting class and the culmination of it was to write a one-act play, and he just started writing a movie which with the help of Ben Affleck became this movie.
On The Graham Norton Show (2007), Harvey Weinstein revealed that when he first read the script there was a scene were Sean and Gerald give each other oral sex. Weinstein questioned Matt Damon and Ben Affleck about this and they responded that it was written as a gag to make sure he actually read the script.
When Robin Williams and Matt Damon were shooting the scene on the bench in the Public Garden, in the movie it seems like they're the only people in the park. Robin Williams being a massive star, there were at one point with over 3,000 people out there, watching that scene.
The Ontario Specialty Company at 133 Church St. Near Queen street in Toronto Ontario was the setting for Matt Damon and Minnie Drivers date. The real life manager of the store Anna Zejn makes an appearance.
After Matt Damon and Ben Affleck sold their script to Castle Rock, it was printed in Daily Variety that they were going to get $600,000 on it. By using a copy of the Daily Variety, because Affleck and Damon had no credit at the time, they rented this house that was $3,000 a month.
After Matt Damon and Ben Affleck removed the NSA stuff from the script, Castle Rock -by that time owing the rights to the script- gave them time to go out and find somebody who will buy their version of the movie, meaning a director. But there was a price tag: Castle Rock wanted to get their money back. So if they couldn't find anybody to buy it, when it came back to Castle Rock, they were not going to be the stars anymore.