[4] Based on the Furlings characters created by Rae Lambert, the film was directed by Charles Grosvenor and produced by David Kirschner, and stars the voices of Michael Crawford, Ellen Blain, Benji Gregory in his final film role, Paige Gosney, Will Estes, Janet Waldo, Elisabeth Moss and Ben Vereen.

The film is about a trio of "Furlings" – the story's term for young anthropomorphic animals – who go on an expedition to cure their poisoned friend.

It's tire is punctured by the piece of broken bottle and the ensuing blowout causes the truck to skid off the road and slide down to the bottom of the hill.

The tank of Poison Gas is ruptured in the process and begins leaking into the forest, instantly affecting the foliage.

Desperate to find them, she fails to heed warnings from the others and runs into her home, unknowingly breathing in the deadly gas fumes within.

Because the gas destroyed the plants nearby, Cornelius tells them they will have to journey beyond Dapplewood and bring back the herbs before the moon is full in two days' time.

Their first night they catch the attention of a ravenous one-eyed barn owl after Abigail recklessly leads them over an open field.

He briefly captures Abigail but she escapes his nest using Cornelius' magnifying glass to frighten him, and they manage to find a safe place to hole up.

Edgar stands up to an arrogant bully of a squirrel named Waggs, who keeps insulting Michelle, and they easily find a field full of Eyebright.

Once Upon a Forest was conceived as early as 1989, when the head of graphic design at ITV Cymru Wales (at the time known as Harlech Television, HTV), Rae Lambert, devised an environmental tale entitled A Furling's Story as a pitch to the American cartoon studio Hanna-Barbera (owned by Turner Broadcasting since 1991), along with partner Mike Young.

Thanks to screenwriters Mark Young and Kelly Ward, the project started as a made-for-TV film with The Endangered as its new name.

[3] At the suggestion of Liz Kirschner, the wife of the film's producer, The Phantom of the Opera's Broadway star Michael Crawford was chosen to play Cornelius.

While filming the live-action references, the crew "was thrilled beyond [...] expectations [as the chorus] started flipping their arms and moving their tambourines", as Kirschner recalled.

William told to The Atlanta Journal-Constitution in May 1993 that it was the "finest feature production [we have] ever done", and was happy that the studio accepted his proposal.

The creator in question was David Kirschner, who served as Tail's executive producer, and actually did create the characters and the story of the film, but ReelViews' James Berardinelli and the Times Union of Albany found it misleading, hoping instead for the likes of Don Bluth or Steven Spielberg.

[7][8] Hanna-Barbera's feature production unit created to produce this film and Jetsons: The Movie (1990), which also carried an environmental theme, was spun off into another unit under parent company Turner Entertainment, Turner Feature Animation, which produced The Pagemaster and Cats Don't Dance.

The critical consensus reads: "Inert animation and generically chipper characters rob Once Upon a Forest of any personality despite its well-intentioned message and critter appeal for very young children".

[16] Once Upon a Forest was adapted into book form by Elizabeth Isele, with illustrations by Carol Holman Grosvenor, the film's production designer.

The tie-in was issued by Turner Publishing and distributed by Andrews McMeel, a month prior to the film's release (ISBN 1-878-68587-2).

The multimedia company Sanctuary Woods also released a MS-DOS point-and-click adventure game based on the film, on CD-ROM and floppy disk for IBM computers; Beth Agnew served as its adapter.