The movie's Chinese version, which has pop idol Wang Yuan sing the end credit song, casts actress Song Zu'er and actor Zhang Xincheng to voice for the two protagonists.

During an interview with China Daily, director Peter Sohn says that his original idea for the story started seven years ago when he drew a little doodle and became fascinated with the concept of how fire and water could be connected.

After pitching his idea to decision-makers and fellow animators at Pixar Animation Studios, the veteran director, who has been working there since 2000, recalls that they were intrigued by his pitch but did not entirely understand the concept of the story.

Throughout years of character and plot development, the movie gathered input from more than 100 first- and second-generation immigrants working at Pixar. They shared their personal experiences, which injected the story with a depth that explores how people from different cultures handle their differences, and sometimes, frictions.

Cultural metaphors are prevalent throughout the movie. Lumen's parents, also immigrants from a remote city belonging to the Fire "race", take a ship voyage to begin a new life in Elemental City. Despite growing up in a culturally diverse environment, Lumen is asked to make a promise to marry a fellow Fire member before her grandmother passes away.

This scene is inspired by the real-life experiences of the director. Sohn's parents emigrated from South Korea to the United States in the 1970s and held a family belief that Sohn, who was born and raised in New York, should marry a woman of Korean descent.

"It was crazy when I was in high school. When my grandmother was passing away, we were all around her. She suddenly said in Korean: 'Marry a Korean!' And then she passed away. It created a lot of pressure for me growing up, especially when I fell in love with someone who wasn't Korean," recalls the director, whose wife is an Italian-American.

As Sohn has transferred his youthful memories into inspiration for the movie, he has also faced many challenges in visualizing the Elemental City — a work of fantasy that requires everything to be built from scratch.