While living in the Australian surfing village of Byron Bay in the late 1970s, Wayne Young had an unhip idea for an animated children’s movie about the rain forest. Young’s wife at the time, Diana, told their children bedtime stories inspired by the subtropical woodland around them, home to platypus, kookaburra, luminescent mushrooms, and more (“basically unbelievable,” Young says). That tale, about a tribe of fairies living in endangered nature, would make a great children’s movie, Young and his wife thought. “But,” he says, nearly 40 years later, “we had to wait until Hollywood star power got behind the environment.”

It took a decade—and the fortuitous casting of Robin Williams—for that moment to arrive for Young, and for FernGully: The Last Rainforest to begin its journey from animation underdog to millennial touchstone. By the late 1980s, the environment had become a cause célèbre for celebs: Sting appeared on the cover of Paris Match with an Amazonian tribe chief, and Madonna threw a benefit concert in New York called “Don’t Bungle the Jungle.” On Earth Day in 1990, a shaggy-haired Tom Cruise delivered a speech at a D.C. rally—“Have you planted a tree? Do it!”—which was broadcast by all major networks.

“That was our window of opportunity,” says Young, who had, in the interim, produced 1986’s hit Australian export Crocodile Dundee and arrived in L.A. to shop an animation studio at not quite the right time. The Disney Renaissance, which saw 1989’s The Little Mermaid reinvigorate the market for animated films, hadn’t yet revealed itself. “There were very few outfits doing Disney-quality animation, and the ones that did were not at all interested in outside projects,” says FernGully director Bill Kroyer. “I look back and can’t believe we did it.”

Kroyer, a Disney veteran and Oscar-nominee for the seminal animated short Technological Threat (1988), had started Kroyer Films with his wife, Susan; their company grew from 16 to about 40 animators to work on FernGully, its first feature, with a script from Jim Cox, who’d recently written the first two treatments for Disney’s Beauty and the Beast.

“The pitch was that the real rain forest is so magical itself, that’s the thing you want to portray, to convey that it’s worth saving. We didn’t draw fantasy plants or animals—we saw these things,” says Kroyer, who led the team on a seven-week research trip in the Australian rain forest. “We went over there with a thin story, but everything came together when we saw the glowing fungi.”

They set up studio in a former brewery complex in California's San Fernando Valley. Across town, in Burbank, Jeffrey Katzenberg, some six years into his fabled tenure as the willful head of Disney’s animation wing, did not fail to notice the arrival of the outsider Aussies. “Jim took me on a tour at Disney with someone else’s name on my tag and pointed out the young guns to hire for FernGully,” Young explains. “Katzenberg wasn’t happy when he found out. He was behind all the aggravation that Disney caused us: twice we rented facilities, and they gazumped us by paying more. When we found space in the brewery, Disney tried to buy it. One day Katzenberg and eight or so others marched through to inspect the premises—we scrambled to cover everything up! But it was also really about Robin.” (Katzenberg declined to comment for this article.)