From the Super Mario Wiki
Ameboid is an enemy that can be found at the gate from Smithy's Factory in Super Mario RPG: Legend of the Seven Stars. It has low HP, but if Mario and company fail to defeat it in a single attack, Ameboid splits into five with the same stats as the original. Outside of battle, they are merely small blue spots that become bigger and reveal themselves to be Ameboids when they are approached. They are strong against jump attacks and weak against fire.
Ameboids are named after Amoeboids, which are amorphous unicellular organisms. The enemy's appearance and behavior (being able to split into multiple individuals) also suggest actual Amoeboids.
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