This video of Robin Williams and Ben Stiller helping their teenage co-star get a date to the prom has gone viral.
Gisondo plays Stiller's son in the film, which was released in the US last week.
"All morning, Robin was pitching more ideas. He was saying: 'Can I say this? Would it be appropriate to say this?'" Gisondo told the Hollywood Reporter.
The teenage actor added: "It turned into this three-minute, ridiculous thing. A prom-posal."
And the video was a success: Gisondo got a date to his senior prom.
Commenting on what it was like working with Williams, who died in August, Gisondo said:
Robin was this bottomless reservoir of kindness and hilarity.
It was juts so special to work so closely with this guy who's movies I've grown up with and watch his preparedness and his kindness.