Michael Crawford has stated he had a terrible time singing the song "Please Wake Up" as it was a grown-up singing to a child who was on the verge of dying. He had to struggle not to cry while recording.
The last Hanna Barbera production to be released theatrically.
It was the Fox company's choice to change the title of this movie from "The Endangered" to "Once Upon a Forest". Fearing audiences would find the former title too sensitive for a children's film.
The scene where Abigail was dragging the comatose Michelle from her gas-invested home has the similar music background from Feivel, der Mauswanderer (1986) (the scene where Fievel was washed down in a hole as the firemen were putting out the fire near the end of the movie) and In einem Land vor unserer Zeit (1988) (the scene after Littlefoot's dying mother saves Little Foot before the earthquake), both scores were also composed by James Horner.
One of the deleted scenes featured the voice of Glenn Close, whose character was removed entirely from the final storyline.