Require context, and some up-front effort
I personally do not know if "How could Pikachu function" would be accepted on the scifi stack exchange. For one there's that site having a different approach - it is defined by its contents, rather than the answering approach, in which Worldbuilding seems quite unique. "How does the Force work?" is a question that can be answered with nothing but references to canon. "How would this Force-like magic system work?" requires creative input, and it is one of the joys of this site, as I experience it.
Similarly, "Why do redshirts die?" has a canon answer: they're used for security. In contrast, the brilliant answers to "Why does the Conjoined Alliance of Space Travellers keep producing red uniforms?" lists wonderful possible alternative and highly creative reasons as to why some crewmen wear red. It is rightfully one of the most popular questions on the site. Such answers however go directly against established
Star Trek Stellar Trip canon, and would not be as appreciated on the other site.
So I think there's definitely a case for asking for stuff similar to existing works - it just should not require a "canon" answer. In fact, those should be discouraged. "Well, in the show Star Trek redshirts die because they are in security." would be a valid answer to the linked question, but not necessarily the best one. I do not know if Pokémon explains where Pikachu's powers come from, but if it or some ancillary work does, the SciFi site would treat that as the answer, and Worldbuilding as an answer.
So, instead of banning the genre outright, I would just require more effort to be put into questions asking about existing media, and specifically giving it more context that defines the creature or element more narrowly than the source material does. So a slightly more valid Pikachu question would be like this:
What's the closest you could get to a Pikachu within these parameters?
A basic Pikachu has these qualities:
Now, I have a world where their electricity should be purely biological or they evolved with their general shape and colourations until magic came and added the electric powers or the creatures are domesticated by humans yet they will eagerly fight their own kind or one or more other things that narrow the query down from "poof me this thing into existence".
The last thing is the most important. Creature design should have a narrower scope than "how it is depicted in traditional media", which is vague and unfair to those unfamiliar with said media. And a creature design question should be more than a list of qualities, it should also give an angle, the questioner's take on the creature. Best would be if they already have some idea on how a rodent could channel lightning, and asked to have it verified; but I also like more open-ended questions.
As long as you further narrow it down from the source material, existing IP questions are fine with me. If the source material has already defined the thing and its history precisely, then you can ask a broader question instead, such as: "Could mammals evolve electric powers?" - which would no longer be an Anatomically Correct question.
tl;dr: require more than a list of bullet points, require context and an angle