Set in Spain during the Age of Exploration, the film followed Jack as he discovers a world of giants hidden within clouds. Jack befriends the female giant Inma, who's "11 years old, 60 feet tall, fiery, feisty and a lot to control" and treats him like a living doll, Greno said. Meanwhile, the antagonists, Storm Giants, stand at 120 feet.
The film was officially announced on August 14, 2015, by John Lasseter, at the D23 Expo. The film is set to be a musical, with songs written by Kristen Anderson-Lopez and Robert Lopez, who previously wrote the music for the Academy Award-winning film, Frozen, in 2013. The pair won the Academy Award for Best Original Song for "Let It Go". Dorothy McKim, who produced the acclaimed short Get a Horse!, was announced as the producer of the film.
On October 3, 2016, writer Meg LeFauve was announced to join the film as a co-director alongside Greno.
On April 25, 2017, Disney announced that the release date had been pushed up to November 25, 2020, from its previous release date of November 21, 2018.
- Gigantic was pushed back to 2018 in 2015 and was originally set to be entitled Giants.
- Among Duke Weaselton's bootleg discs in Zootopia is one for an animal version called Giraffic, with Jack, played by a squirrel, climbing a giraffe neck instead of a beanstalk.
- Gigantic was originally scheduled to be released on March 9, 2018. However, on June 30, 2016, Walt Disney Animation Studios announced that Ralph Breaks the Internet: Wreck-It Ralph 2 would be released on that date, and Gigantic would launch instead on November 21, 2018. The film would be delayed again for a 2020 release, after Ralph Breaks the Internet: Wreck-It Ralph 2 took the previous November 21, 2018 release., until eventually being pulled from Disney's film slate.