Trivia: That puppet was SO large that it moved slow as dirt. That means, every actor had to act in slow motion while around the puppet. This included the musical segments. 

@tenaflyviper Confirm?

This is absolutely true.  The Audrey II was played by varying sizes of animatronic puppets.  Each of the vines was actually free-moving cable that was revolutionary at the time: There was nothing holding them up–they were designed to support their own weight while in operation.  All scenes with the larger Audrey II were shot at a slower speed, including the musical numbers.  This means that every actor you see interacting with it was performing at roughly half the speed you see on the screen, and it was sped up in post-production.  This technique is what made it possible to capture all of the many motors operating Audrey II’s lips in a way that looks impressively natural.