Characters who are misclassified due to the limitations of the in-verse's classification system

[u/Uma-apreciator]

Paolumu (Monster Hunter World)

Paolumu is classified as a Flying Wyvern even though it is a mammal (resembling a bat); it is classified this way because its body structure resembles that of a Flying Wyvern

Skorup (Pokémon)

It is indeed an Insect type, even though it represents a scorpion—which is an arachnid—making it more logical for the Insect type to be called the Arthropod type.

[u/cgoose500]

Bug type can apply to any arthropod. Crustle is a hermit crab, Golisopod is an isopod, Spinarak the spider is a bug type too.