How Robin Williams pranked co-star in "Good Will Hunting"

After Robin William's death Monday, many celebrities have spoken out on the profound impact the actor had on their lives and on the Hollywood community.

Harvey Weinstein, Co-Founder of the Weinstein Company, worked the actor firsthand.

"It's been a tough week, you know, to collect your thoughts and to think about those implications," Weinstein said on "CBS This Morning." "Because, when you knew Robin, he made everybody else's life so good. He was just so funny and so bright ... and if you made a movie with him, he was so good for the crew."

Weinstein said his fondest memory of Williams was on the set of "Good Will Hunting," in which the actor ad-libbed a scene with Stellan Skarsgard.

"So it was like his [Skarsgard's] first role, he had just gotten off the boat from Sweden. He's a very famous actor there. Never did an American movie," Weinstein said. "And Robin says to Gus [Van Sant] and me, 'Let's welcome him to America. I'm going to change the script, and Gus, you tell him it's all about improvisation.'"

Weinstein says Williams began impersonating different Hollywood actors instead of following the script.

"So here's this scene about mathematic formulas, and Robin comes out and goes, 'Jack Nicholson.' And then he does Jack Nicholson. And then Gus, he's pointing to Stellan, and he's in a state of shock like a deer, and then he does Jack and he does Bob DeNiro doing the scene, and he's like doing 15 things, and the crew is totally straight-faced while Gus is shooting, and then Stellan starts to ad lib this Swedish gibberish, because he's so lost in the scene," Weinstein said. "And then when Gus yells 'cut,' 180 members of the crew exploded with laughter, and Stellan looked around and goes 'What happened to me?' And Robin told him what was going on."

Weinstein says this instance was just one of countless examples of the fun-loving spirit Williams brought on and off set.

"Every day was like that with him," Weinstein said. "I think for Billy Crystal and Robert DeNiro, and there are people that were so close to him, I just, you know. I emailed Billy last night. It's just too tough for a lot of people to deal with. This is just, a shock."

Aside from the joy he brought Hollywood, Weinstein says Williams will always be remembered simply for his quality acting.

"We'd give him one scene in 'Good Will Hunting,' we'd say, one for Robin, one for us, where he'd do the script," Weinstein said. "But inevitably there was always something that he added to that film, right on the spot. Just a brilliant mind at work."