hmmm…I was never really tried to actually identify “species” in Arthur though I watched it a lot with my children when they were younger. For example, the difference between dogs and cats was almost impossible for me to discern. I must compliment you on your research to put together the “species chart” for the different families. I did not know who was “what” unless it was explicitly spoken with even Ratburn not necessarily being a rat in my mind. I did not really care that much, they were just “generic mammals” to me.
This was purposeful I thought, because it indicated that “species mixing” ended up making everyone look a little bit alike and on the other hand still a little different. I don’t see separation but an amalgamation of diversity, because that is where we as a society SHOULD be going. To become “color blind”, we need to be able to watch a show like Arthur and accept it for the interplay of the characters and be “species blind”. I think Arthur actually helps children accept their differences and recognize how much alike we all actually are.
Besides that I think the target audience age is really on the cusp of having to deal with things like love as it relates to “sexual love” versus “procreation” or just “doing it” for fun. There is quite a bit of complexity there that parents would like to avoid until “life” requires their children wade into that quagmire.