How an MIT Professor Helped Good Will Hunting Get the Math Right—and Landed a Tiny Role in the Film

Image via Good Will Hunting

On June 3, filmmaker, activist, and native Cantabrigian Matt Damon will be the guest speaker for the 2016 MIT Commencement. In 1998, Damon won an Academy Award and a Golden Globe Award for co-writing the screenplay of Good Will Hunting, where he played an MIT janitor with genius-level intellect. Learn more about MIT Commencement and how you can watch his speech.

In spring 1997, Professor Daniel Kleitman received a phone call from someone asking if he would talk to two men who were writing a movie screenplay about a genius-yet-troubled mathematician. Kleitman agreed and met with the screenwriters a few days later. The two men, it turns out, were Matt Damon and Ben Affleck and the film was Good Will Hunting.

“When Matt and Ben showed up at my office, I had never heard of them,” Kleitman says. “They looked like college students. I thought to myself, ‘They’re making a movie. That’s nice.’”

And Damon and Affleck had a simple request: they wanted to hear mathematicians talk about mathematics, so the dialogue they would write in the move would sound authentic.

“When they asked me, ‘Can you speak math to us?’ my mouth froze,” he says. “I felt silly mumbling random math so I found a postdoc, Tom Bohman. We went down to the old math lounge in Bldg. 2 and I gave a quick lecture. They took notes, but they didn’t really know what we were talking about.”

Damon also inquired about a plausible equation that the main character could solve in the movie, and Kleitman and Bohman suggested the computer science problem P = NP. (An adjacency matrix was eventually used in the film.)

Kleitman didn’t expect much to come from the meeting. “I was skeptical this would actually be made into a movie,” he says. But a few months later, the movie’s production company offered him a role as an extra, and Kleitner can been seen in the background of one the movie’s iconic scenes: the first kiss between Will Hunting and Minnie Driver’s Skylar Satenstein at the now-defunct Tasty Sandwich Shop in Harvard Square.

In the video above, Kleitman can be seen at the 1:48 mark and again at the 2:18 mark.

“We walked back and forth outside the Tasty for hours,” Kleitman says. “It was close to midnight and I was hungry. I walked across the scene, then realized the food was on the other side. So I walked right back and that was the scene they used for the movie! Luckily no one was watching the background when they kissed.”

Kleitman’s connection to the movie came via a recommendation from his brother-in-law, Harvard Professor and Nobel Prize-winning physicist Sheldon Glashow. The script’s earliest incarnation had Will Hunting as a physicist, but Glashow insisted that a mathematician would be more plausible, and suggested that the duo meet with Kleitman.

“Before I saw the movie, I was worried that the math scenes in the movie would be foolish,” Kleitman says. “But when I saw the movie, I said, ‘They didn’t screw it up!’ and I remember being very pleased.”

Image via Good Will Hunting

Kleitman, now a professor emeritus at MIT, would receive a Thank You in the film’s credits and attend the premiere party at the Burren pub in Somerville. He reconnected with Damon and Affleck, who apologized for any incorrect math that might have appeared in the film. And despite the success of the film, Kleitman had no ambitions to make the switch from math to movies.

“When the movie premiered, the Boston Globe review mentioned that it went far to get the math correct and even the extras looked authentic,” Kleitman says. “And since the screenplay won the Academy Award, and the extras were positively reviewed, I figured I would retire while I was on top!”