As part of her preparation for the role, Jodie Foster read the same books that François Truffaut read when he was prepping his similarly themed film The Wild Child (1970). Foster, being fluent in French, read them in their original language.
Jodie Foster originally planned to direct the film herself, but turned it over to Michael Apted instead.
The source play, written by Mark Handley, tells the story of Poto and Cabengo, twins who had developed their own secret language. It's based on his experience living in the Cascade Mountains in the 1970s.
A successful four-membered South Korean indie-rock band named themselves Nell after this movie.