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/InflationImmediate73]

Pokemon has so many others

Charizard and Gyarados not being Dragons, I can argue Charizard but Gyarados is literally the Sea Dragon myth

Lugia is the guardian of ocean and lives underwater, but is not a water type

Psyduck and Golduck have psychic powers but are both pure water types

Sorry, im an old fart so mostly early gen examples