I just watched "The Muppet Musicians of Bremen" that I taped about 10 years ago when Nickelodeon had "Muppet Matinee". The puppetry on it is amazing. Except for a few shots where you can see the strings on the marionettes, all the characters are completley life-like, more than any computer animation I have ever seen. There are only two recognizable voices in the cast, Jim and Jerry, but Frank and Richard did additional characters as well. It seems almost every Muppet special featured a puppet which would become a main character. For the Frog Prince there's Robin and Sweetums, Tale of the Bunny Picnic- Bean Bunny, Mr. Willowby's Christmas Tree- Bobo, and for this one, one of the rats would be become Rizzo.