Anne Hathaway was the first actress to sign on at a time when the project had no financial backing. She heard about the script after finding herself "in a little bit of an artistic no man's land" for inspiration. Director Jonathan Demme screened for her a copy of A Field in England (2013), after which Hathaway decided that it represented exactly the type of movie she wanted to make. After asking her representation to see a similar script that she could join, she was sent the Colossal script. Hathaway found herself attracted to the genre-hopping nature of the script, later comparing it to Being John Malkovich (1999), one of her favorite films.
No motion captured footage was used for the creation of the monster; rather, footage of Anne Hathaway acting out her parts was given to the CG team, who used this as reference points. The CG artists, as opposed to Director Nacho Vigalondo, were responsible for the look of the monster itself. Vigalondo stated that this was partly due to his lack of artistic skill and partly due to him "[wanting] them to feel like characters that felt like a part of the genre we're playing with."
Prior to the start of filming, Toho brought a lawsuit against Voltage Pictures, the film's producers, for unauthorized usage of Godzilla's image in emails and other promotional activities, allegedly to raise funds for the film.
Also broadcast on Australian Television under the title "Do not hesitate."