New details have emerged of how the brilliant Robin Williams brought his character of Mrs Doubtfire to life on the big screen in such a spectacular way.
The much-loved movie, which is based on the novel Madame Doubtfire, came out in 1993 and saw Williams star as a struggling voice actor called Daniel, whose life is in turmoil after his divorce and losing custody of his children.
He comes up with a fantastical scheme to be able to spend more time with his children by dressing up in drag as a Scottish nanny, who his ex-wife Miranda (Sally Field) hires to look after the little ones.
Tragically, Williams died in August 2014 having taken his own life, but his memory lives on fondly in fans of the film. Now, director Chris Columbus has shared more information about the process of creating the movie in honor of its 30th anniversary.
The late Williams was known as one of the greatest comedic actors of all time, and Columbus has revealed the unbelievable improvisation process that made his characters what they were.
In honor of Mrs Doubtfire's 30th anniversary, Columbus told Business Insider that around two million feet of film were shot while making the movie, and he needed "four cameras" running at all times to "keep up with" Williams.
He revealed that Williams would call him "boss" or "capo" on set, and told him: "Early on in the process, he went to me, 'Hey boss, the way I like to work, if you're up for it, is I'll give you three or four scripted takes, and then let's play.'"
By that he meant improvise, and Williams would then take each scene and give it its own spin, which Columbus says was "something to behold".
In fact, the only way to get Williams to stop improvising new takes was when the cameras eventually ran out of film, given it was before the digital age.
Columbus explained: "If it were today, we would never end. But back then, we were shooting film so once we were out of film in the camera, we would say to Robin, 'We're out of film.' That happened on several occasions.
"It got to the point that I had to shoot the entire movie with four cameras to keep up with him. None of us knew what he was going to say when he got going and so I wanted a camera on the other actors to get their reactions.
"For Pierce Brosnan and Sally Field, it was quite difficult for them not to break character."
He revealed that he still has "972 boxes of footage" in storage from the filming of Mrs Doubtfire and hopes that one day some of it might be shared with the world in the form of a documentary.
Some of his favorite improvised scenes in the movie include Mrs Doubtfire's fake teeth slipping out of her mouth and into her wineglass, leaving the other diners at the table mortified.
The nanny then started trying to fish the teeth out of the glass with a fork before joking: "Carpe dentum, seize the teeth."
Columbus added: "And the second one that stands out is what I call the pie-in-the-face sequence. It's when Mrs. Sellner (Anne Haney) comes to Daniel's apartment and he's going back and forth as Mrs. Doubtfire and Daniel.
"When he's in the bedroom putting on the Doubtfire costume, that probably was his hardest work on the film. Verbally and physically. He was physically spent after doing that. I think we did 18 takes on that sequence."
With so much footage existing from unused takes of the movie and behind-the-scenes footage, Columbus hopes to one day hire an editor to go through the reams of footage to create a documentary allowing people to see the genius at work.
He added: "We want to show Robin's process. There is something special and magical about how he went about his work and I think it would be fun to delve into it."