So in a previous post I hypothesized that Jr. Troopa could be a Magikoopa due to his ability to wield magic.
Then I wondered if his Japanese name would give any indication to this.
Turns out his Japanese name was not Kamekku or any variation of it. Nor was it Kokamekku, or even NokoNoko.
Instead his Japanese name was Kowappa aka Brat Bowser.
This would mean he is actually a Kuppa, a species of turtle in the Mario World that I have talked about before.
This would also explain why he seems to have access to magic so easily, since it seems to be something reserved for the Kuppas/Bowsers and Magikoopas.
So the boss named Spiked Koopa who is a member of the Brown Sugar Pirates is not a actually Koopa, but rather the species Hammer Bros. are a part of.
This is because in Japanese his named does not contain Noko or NokoNoko, but rather is Toge Burosu meaning Spike Bro.
Due to his shell being a different model from typical Bros. Shells, he is able to retract inside of it and uses it in boss fights.
While some people have suggested turtles like Hammer Bros. are Koopas, it hasn't actually been stated to my knowledge.