Veteran primate choreographer and actor Peter Elliott actually met and worked with Nim Chimpsky when he was researching chimpanzees for Greystoke: La légende de Tarzan, seigneur des singes (1984). He also met and worked with another famous signing chimp by the name of Washoe.
As of 2019, this has been James Marsh's last documentary. Since Projet Nim (2011), he has enjoyed a run of well-received feature films like Des ombres au soleil (2012), La théorie de l'univers (2014) and Le jour de mon retour (2018).
James Marsh became interested in the story of Nim when his L'homme sur le fil (2008) producer Simon Chinn brought Elizabeth Hess' book to his attention. Marsh was particularly interested in telling a story that was devoted to the life of an animal.
James Mahoney, the chief vet at the laboratory where Nim spent some of his later years, was very reluctant to be involved in the film, given that this period was probably the most traumatic for Nim during his 26-year life. He was convinced by director James Marsh that he would not be depicted as the film's villain as Marsh had no interest in getting into the minefield subject of animal rights.
For reference points, director James Marsh watched other animal-focused documentaries and features, like Barbet Schroeder's Koko, le gorille qui parle (1978), Frederick Wiseman's Primate (1974) and Robert Bresson's Au hasard Balthazar (1966).