I can't help but wonder if including an image of Muppy on the Rufus page might have been done on purpose, as a joke on how the book says they hate being mistaken for each other. Though if it was a joke, it's probably lost on casual readers who don't even know either character.
I know that Shemin made a list of over 200 characters to include, which Disney shortened. I'd like to know which characters he's most surprised Disney objected to, and which he's least surprised Disney didn't object to including. Of the characters who did make it into the book, I'm most surprised about Splurge, Rufus, and Spa'Am.