I'd like to help you on this list, too!
I don't think "The Clown" should be added to the list. She was just a filler, when Big Bird needed a clue to where he was going. Ditto to "B.B. King's Back-Up Singers". They sang as much as Bert, Big Bird, Baby Bear, and Benny Rabbit, and were just two A.M.s needed because a verse mentioned: "we couldn't have a beard".
The Three Men In a Tub can be in a group, but each member is identified, like your list of "The Count's Classmates". Here's the descripts:
BUTCHER--Pointy green AM with lavendar eyelids on his vertically oval eyes, light blue nose, and short brown hair. He wore a white butcher's hat and apron, and a vertically striped blue and white shirt. He wore a string of sausages around his neck.
BAKER--Fat blue AM in a baker's outfit. He has scraggly gray hair, a moustache, a green nose, and orange eyelids.
CANDLESTICK MAKER--Short lavendar AM with fuzzy brown hair and beard. He has an orange nose and blue eyelids on his vertically oval eyes. Not sure on his outfit, but he looked a bit like a colonial candlestick maker. Can't help you much there.
Speaking of "group listings", you may want to consider a list of "Elmo's World" Muppets, since there are many "object" Muppets built for it. Example:
"Elmo's World: The Bicycle"
"Elmo's World: The Helmet"
The Muppets in Jimmy's Family are as follows:
JIMMY--small pink AM with short dark brown hair and pink eyelids. His black pupils are a bit bigger than normal Muppets, and I think he wears white and orange pajamas.
JIMMY'S FATHER--tall orange AM with short black hair, blue oval nose, pink eyelids, a white shirt, and red sweater.
JIMMY'S MOTHER--short lavendar AM with a green nose, sleepy eyelids with lashes, and curly light brown hair. Not sure about her clothing, though.