We all know Robin Williams was one of the funniest men in Hollywood and we all probably knew he had a heart of gold, too. The comedian died earlier this year but it seems that even during shooting on one of his final projects - Night at the Museum: Secret of the Tomb - Williams was still on top form.

Night at the Museum 3Robin Williams [R] and Ben Stiller [Bottom left] made one young guy very, very happy

Skyler Gisondo, who played the son of Ben Stiller's character in the movie, was away from home when his friends were asking girls to the prom in the U.S. Unable to ask his fate face-to-face, Skyler called upon Williams and Stiller to do the work for him  - telling the Hollywood Reporter that it was "the most awesome three minutes of my life."

More: Is Night at the Museum 3 any good? Meh.

In a video filmed for Skyler's date-to-be, Williams and Stiller burst onto the screen with a "yo! Yo! Yo!" while wearing a beanie hat and jackets. "Yo Hilary, will you go to the prom with my man here, my man Skyler?"

"All morning, Robin was pitching more ideas," said Gisondo. "He was saying 'Can I say this? Would it be appropriate to say this?' You're Robin Williams. You can say whatever you want!"

Ben StillerBoth Williams and Stiller star in Night at the Museum 3

"It turned into this three-minute, ridiculous thing. A prom-posal. I realised that was the most awesome three minutes of my life and I've accepted it will go downhill from there."

More: watch a video of Ben Stiller and his co-stars at the Night at the Museum 3 premiere

He added: "Robin was this bottomless reservoir of kindness and hilarity. It was just so special to work so closely with this guy who's movies I've grown up with and watch his preparedness and his kindness."

Unsurprisingly, the girl accepted Skyler's prom-posal and the pair went off to the prom. Robin would have been proud.

Night at the Museum 3 is one of the big hitters released for the Christmas box-office this weekend, going up against Annie and Lord of the Rings: Battle of the Five Armies. 

Williams' final work, Absolutely Anything with Simon Pegg and Kate Beckinsale, is set for release in July 2015. It tells the story of a teacher who experiences a series of mishaps after discovering he has magical powers.

Watch the trailer for Night at the Museum 3: