Here's another animator you can add to your list.
I visited "The Vision of Jim Henson" exhibit in 1999, and it had some of the original sketches for the animation segments, including a picture of Jim putting the rocks together for the number 12 film.
But next to it was a sketch of Boy Bumble (originally called Bumble Arty) and the sketch was drawn by Maurice Sendak! Sendak wrote "Where the Wild Things Are".
Remember Boy Bumble? He was voiced by Jim Henson ("please let me in. It's your Boy Bumble") He let 9 swine in his mother's house on his birthday. They drank wine, trashed the place and shouted:
"Cheers, cheers, cheers! May Bumble live 900 years!"
By the way, the "2 little dolls in the little dollhouse" sketch with the cats was filmed using one of Jim Henson's daughter's dollhouses, FYI.