Two users on this forum (Earwig and Dark Bunny) have referred to something called the "Arthur TV Series Main Model Pack," which was also called the "Original Model Pack." From what I've seen, this seems to be a collection of documents such as Storyboards, floor plans, and character animation sets. Both Dark Bunny and Earwig both seem to have a lot of "Inside Information" about Arthur, so is it possible that they are Arthur producers (or at least have connections to them)?