"[One scene] was pretty emotionally charged, and it was the first time I was ever asked to break down on camera, and we both were breaking down.
"We had to do it over and over again, and the emotion just burst out of Robin."
Clark Duke, 29, who plays Robin's son in the movie, hailed his late co-star a "hero" and was thrilled to work alongside him.
He said: "When you meet one of your heroes, you set yourself up to be disappointed. But he was just so great, and it was kind of surprising just how good of a guy he was."
A Merry Friggin' Christmas - which hits US cinemas later this week - is one of four movies the late actor had worked on before his death that have not yet been released.
Over the Christmas period, he can be seen again as Teddy Roosevelt in Night of the Museum: Secret of the Tomb, which finished production in May and will be released on December 19.
Additionally, the Aladdin star lent his voice to animated pooch Dennis the Dog in live-action comedy Absolutely Anything, which also features Simon Pegg and Kate Beckinsale and will be released some time next year.
A fourth film, Boulevard, debuted at the Tribeca Film Festival earlier this year but has yet to find theatrical distribution.
Watch the trailer for A Merry Friggin' Christmas:
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- Bang! Showbiz