I do remember the Little Shop cartoon. It was from 1991, and was produced by the same animation house that made Muppet Babies. It was a VERY loose interpretation of the original films, though. For one, Seymour, Audrey and Orin were all kids, and the story was set in modern day. The plant was called Junior (in reference, I suppose, to the original 1960 Roger Corman film where the plant is called Audrey Junior), and instead of singing doo wop, he does several rap songs thoughout each episode (he also had googly eyes on top of his head). Obviously the horror elements were left out (hence the abbreviated title "Little Shop"), and making the cast children was a huge cliche that every major cartoon adopted after Muppet Babies originated it (A Pup Named Scooby Doo and Flintstone Kids were around at the same time as Little Shop). The most positive aspect of this cartoon was in its design. It looked like the show's animators adopted the classic look of the old 60's cartoons (think Rocky and Bullwinkle, or any old Hanna Barbera cartoon), which is kind of a tribute to the era that the original films were set in. But everything else about this show was pretty lousy, and strayed too far from the original concept.
And just as a point of interest, Jonathan, my girlfriend played Audrey in her highschool production of Little Shop of Horrors, and a doo wop girl in her college production of the show. I know she had a lot of fun, so I'm sure you're having a great experience working on it as well. From one Little Shop fan to another, break a leg and have a great performance!