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1/12. According to Matt Damon, Robin Williams’ best addition is the last line of the film, which was completely off-script.
2/12. Gus Van Sant painted the picture that hangs in Sean Maguire’s (Robin Williams) office.
3/12. 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
4/12. 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.
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5/12. 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.
6/12. 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.
7/12. The lecture hall in the movie is actually a lecture hall in McLennan Physical Laboratories (MP); a building at the University of Toronto (St. George Campus) in Toronto, Ontario, Canada.
8/12. The scene where Sean and Will are in his office, and Sean starts talking about his dead wife and her farting antics, were ad-libbed by Robin Williams, which is 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.
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9/12. Patrick ODonnell, who says Bull****, you didnt say that in a bar scene, was actually the man behind the maths equations used in the film. He, alongside John Mighton, created the equations and graphic theorems seen on-screen. Our minds are blown.
10/12. 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 Skarsgard, two accomplished actors, doing Damon’s and Affleck’s scene verbatim. They had waited so long (four years) for this to happen.
11/12. 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.
12/12. Minnie Driver’s character Skylar is named after Damon’s girlfriend, Skylar Satenstein, who left Damon for Metallica drummer Lars Ulrich before filming began. Damon and Driver became romantically involved during production.