Sandy Duncan (probably best known for her appearances on game shows) is Peepers.
Executive Meddling: Bluth had to change some potentially scary aspects, such as giving the Grand Duke "Lucky Charm breath" and cutting out a scene of him eating a skunk in a pie. They also made him change wine into "soda" (see below) to avoid a PG rating.
Incidentally, the Skunk Pie sequence was cut not because the idea of an evil giant owl threatening to eat a live baby skunk in a pie is inherently scary in itself (even though it is). It was cut because of a note Bluth's studio received from the preview audience. The scene was too scary and had to be cut because "most cases of child abuse happen in the kitchen, and involve baking instruments".
Somebody along the line (some point the finger at Bluth himself) decided we needed to see the final live-action/animation sequence in an attempt to cash in on the success of Who Framed Roger Rabbit. Goldie was an attempt to replicate the sex appeal of Jessica Rabbit — except that by making her a bird (some animals just... don't make for Cute Furry Girls), he creates a whole slew of other problems. And then he still had to censor Goldie to cover up many cleavage shots and skimpy costumes.
What Could Have Been: The film was originally pitched at Disney as Chanticleer and Reynard, which would have been a crossover between the myths about Reynard the fox and Chaucer's Chanticleer fable. Instead it was rejected, and after being in Development Hell for several years, was snatched up by Bluth.