A quick revision about the animation principle of Appeal:
Appeal in animation can be looked at in 2 basic parts:
1. Design Appeal = the character designs look nice, or 'cool'. The layouts or 3D environment look great. That is one form of visual appeal.
I think of it as looking at an animation movie poster and responding with "Wow, that looks good, I'd like to see that."
2. Motion Appeal = The more important form of appeal in animation (for me) is related to how things move.
For instance, a character design is not appealing (e.g. a character representing a piece of snot). But the way an animator animates that character, can make it move in an appealing, interesting way. I imagine a snot character would be great to animate with lots of stretch and squash, for example.
I really find the animation of Pocoyo appealing, in terms of motion. Some may say the design is simple (I find it appealing), but it is the appeal in the animation that captures my interest: http://www.youtube.com/user/pocoyotv
So if we add Design Appeal + Motion Appeal = VISUAL Appeal; the animation principle of Appeal.
Have you found any other descriptions in your research? Let me know what you find.