The daughter trope of Our Monsters Are Different and Call a Rabbit a Smeerp. So your characters are on an adventure in a Magical Land, and they naturally run into a mythical creature. Said creature is then identified in the text or dialogue by the name of a similar (or not) mythical being or fantasy creature. Cue a moment of confusion for the viewer. This isn't quite Sadly Mythtaken as the very fact that the writer knows that mythical creatures have specific names implies doing some research. (Sadly Mythtaken is more for The Theme Park Version / Disneyfication of classic myths.)