“Frozen” is one of Disney’s most successful movies, but initial screen tests rated it a flop.

Josh Gad, who voices Olaf, told PeopleTV’s “Couch Surfing” that songwriters Robert Lopez and wife Kristen Anderson-Lopez added in “Do You Want To Build A Snowman?” after viewers complained they couldn’t feel the relationship between Anna and Elsa.

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According to Gad, Lopez wanted a “moment where we really see the girls’ affection for each other early on.”

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“Cut to six months later, when I’m screening the film with my wife and Kristen Bell (Anna) and Idina Menzel (Elsa) and the creatives,” he said. “I turn to my wife, who is the most critical person I know…and she says, ‘This is really, really special.’ And I left thinking, OK, we really hit the mark.”