Well, I'm usually one to VTC on stuff that seems off-topic.. but for the Goofy/Pluto question my reasoning was thus: Anthropomorphic animals aren't a real-world phenomenon, therefore, to some degree or another, they are fantasy (Read as: Magical / other world) or SciFi (read as: uplifted animals, alternate evolution, different dimension, etc.) Disney doesn't seem to have defined which they fall into, but it seems that they must fall into one or the other. (Well, you could also call them transparent metaphors, but they've never been defined that way very well, either.) Where canon doesn't exist, the fanbase often does develop it's own explanations, which often end up as canon years later.
Mork & Mindy falls into the same category, to me, although barely.. They hypothesize the normal world with some elements that, as far as we know don't exit, but might.
Scooby Doo is trickier; my perception of it was always a minor mystery show, simply enacted by cartoons. But, again, you have talking animals, AND later on you have a lot of fantastic elements.
This would be an easier answer, if it was just SciFi SE, but despite the name it's SciFi and Fantasy SE.... And fantasy is a much broader topic. Fantasy can be said to encompass anything 'fantastic', and non-science based.. and SciFi grabs the other side of the house. A case can be made to include most things that aren't about this world, just as it is, as being covered somewhere between those two.
Just my 2c, and I've been wrong before :)