In “Star Wars: The Empire Strikes Back,” our hero Luke Skywalker (Mark Hamill) goes searching for a mysterious exiled Jedi named Yoda on the planet Dagobah, unaware the Outer Rim planet is home to “countless shallow lakes and lagoons and multiple living caves” (via Wookieepedia) — or, as Luke himself calls it much to Yoda’s incredulity, a “slimy mudhole.”
“We wanted Dagobah to be teeming with off-screen life; life that you basically didn’t see,” Ben Burtt explained in his StarWars.com interview. “It was entirely invisible. It was under the leaves or under the bark or something in the trees.”
Among the animal noises Burtt integrated into his sound mix for Dagobah were the cries of woodpeckers from the Redwood National Forest and those of different birds from the San Francisco Zoo. The chaotic and “echoey” sound of the zoo’s fowls in their giant cages helped to create the aural environment he was going for. “When you recorded in there and slowed it way down, way down, the little high-pitched chirps became unidentifiable unknown creatures that sparked your imagination,” Burtt noted.
He felt the chittering of raccoons would only further add to the ambiance, assuming he could find a way to record them. “Animals are noisy and you had to come up with a method of isolating the animal from unwanted noises. […] In the case of the raccoons, they just wouldn’t stop moving,” said Burtt. His solution? To take them to a game farm based just south of San Francisco, where it would be easier to isolate them and keep them in a single place. Once there, however, Burtt said he and the farm’s owner realized they would have to take things a step further than expected.