The Baby Metroid is a significant character in the Metroid video game series, first appearing in Metroid II: Return of Samus. It is the last surviving Metroid after Samus Aran spares it, and it develops a strong bond with her, believing Samus to be its mother. The Baby Metroid plays a crucial role in Metroid II and Super Metroid, driving key plot points and ultimately sacrificing itself to save Samus and the galaxy from danger.