While developing the mouth of the plant for the dialogue scenes and musical numbers, Oz, Conway and his crew struggled to figure out how to make the plant move convincingly. "We kept trying and trying and it didn't work." The solution presented itself while reviewing test footage of the puppet. When the film ran backwards or forward at a faster than normal speed, the footage looked more convincing and lifelike. They realized they could film the puppet at a slower speed, making it appear to move faster when played back at normal speed. "By slowing it down it looked it was talking real fast. We then went 'holy cow, look at that. We can do it. The frame rate for filming the plant was slowed to 12 or 16 frames per second, depending on the scene, and frequent screen cuts were used to minimize the amount of screen time the puppet spent with human actors; when interaction was necessary, the actors (usually Moranis) would pantomime and lip sync in slow motion. The film was then sped up to the normal 24 frames per second and voices were reinserted in post-production. Levi Stubbs' recordings were filtered through a harmonizer when slowed down so that they were coherent for Moranis or Ellen Greene.