WOOT! I have just figured out why Blastoise is called the "Shellfish Pokemon"!
Okay, so, curious if it was a mistranslation, I checked what Blastoise's Japanese Category was. It was simply "Shell Pokemon". Okay, odd, why would the translators call it a shellfish then instead of just shell? Curious about the Japanese word itself, "こうら", I put it into Google and it gave me what it literally says in English, "kōra". I checked what the Japanese word for Shell and Shellfish was, and they were nowhere close to that word ("Sheru" for Shell, "Kai" for Shellfish). So, I typed in Google "what does kōra mean in Japanese" and got my answer:
It was indeed a mistranslation. While ONE definition of Kōra is indeed "shell", the other definition of Kōra:
Carapace. Now it's not wrong to say turtles and tortoise have carapaces, "
carapace" is the more scientific way of describing what we usually think of a shell being (a hardened section on the upper body). However, normally the term is mostly associated with arthropods and their exoskeleton, and that includes crustaceans like crabs, lobsters, and shrimp; also recognized as shellfish.
Still, unless the translation team didn't know what Blastoise looked like or was related to Squirtle and Wartortle (both called Turtle Pokemon), I still don't get why they went with "shellfish". Like, if they weren't sure what translation of "kōra" to go with, why not pick the more ambiguous "shell" or even "carapace"? Of course, I'm saying that 20 years after the fact where just Googling something is the norm, could be whatever the translation team was using to translate the words maybe listed kōra as shellfish or at least as one of its translations.
iirc Magearna's ability to fold into a bal lshape is even in the game as its entrance animation, which is cute.
I think the only "transformation" quirks that a Pokemon is capable of in media but doesnt show in-game is Golurk (able to retract its limbs for both turning into a canon and to rocket around) and the Vanilluxe line (the snow-less version).
We never see a Burmy without its coat in the games though it has been shown in the anime and manga.
"DON'T LOOK I'M NAKED!"