Set in a fantastical world, where the populace once had magic, two teenage elf brothers, Ian and Barley Lightfoot, receive a wizards staff as a prearranged gift from their father, who died before Ian was born and when Barley was too young to clearly remember him. The staff came with a spell that will bring him back for only 24 hours, so his sons can meet him. Prompted by Barley, Ian uses the spell, only to end up bringing back just his father's legs. This causes the brothers to go on a quest for a way to bring back the rest of their father before the time is up.
In July 2017, Pixar announced a "suburban fantasy world" film at the D23 Expo, with Scanlon directing and Rae producing. The film's inspired by Scanlon's father's death when Scanlon and his brother were younger, and their relationship. He decided to write the story after hearing an audio clip of his father. On December 12, 2018, the title was revealed. In 2019, Jason Headley and Keith Bunin were hired to rewrite the screenplay.
On December 12, 2018, Holland, Chris Pratt, Julia Louis-Dreyfus and Octavia Spencer were announced as starring in the film. While having recorded most of their lines separately, Holland and Pratt did some of their recording sessions together since, according to Scanlon, "they've worked together before and hung out together". On December 17, 2019, Ali Wong, Lena Waithe and Mel Rodriguez joined the cast of the film.
On May 29, 2019, two stills from the film, featuring Barley, Ian and their mother, were revealed. The following day, the film's teaser poster was released, and the teaser trailer debuted during ABC's broadcast of the 2019 NBA Finals. The trailer was also shown with Toy Story 4 and Spider-Man: Far From Home. An official trailer was released on October 10, 2019. Another trailer was released on December 17, 2019.