One of Frozen's most popular songs was only added after disastrous test screenings

It seems hard to imagine now given the franchise's incredible popularity, but there was once a time where the success of Frozen was far from a safe bet.

In an interview with People TV, Olaf actor Josh Gad recalled a conversation with songwriter Robert Lopez during production where it became clear that the film was missing something important.

He said: "Bobby looks at me and he goes, 'We just screened the movie and it's a mess.' And I go, 'Well, can you fix it?' He goes, 'I hope so."

The songwriter, who worked on Frozen and Frozen 2 with his wife and creative partner Kristen Anderson-Lopez, explained they wanted a sequence that would show the affection that Anna and Elsa had for each other as children.

To accomplish that, they began work on a little song called Do You Want to Build a Snowman?, which would go on to become one of Frozen's most famous tunes.

Six months later, Gad attended a screening of the re-edited film alongside its creative team and his wife, Ida Darvish, who gave her prestigious endorsement.

Gad added: "I turn to my wife who is the most critical person I know, and she looks at me and goes: 'This is really special, this is really, really special.' And I left it there being like, 'Okay, we hit the mark. We really hit the mark.'"

Frozen went on to become the highest-grossing animated film of all time, making almost $1.3 billion and spawning a popular sequel late last year.

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