Grandma

Grandma is a minor character in the game Super Mario RPG: Legend of the Seven Stars. During the game, she dresses up as the princess so Toadstool can sneak out of the castle and join Mario on his adventure to defeat Smithy and recover the seven Star Pieces. She and Toadstool are the only ones who know about Toadstool's ???.

Relationship with Toadstool
The name "Grandma" could indicate a blood relation between Princess Toadstool and the old Toad. However, it could also be a mere term of endearment. In fact, the name "Grandma" is a literal translation of her Japanese title "Obāsan", which can mean "grandmother" or be used as a respectful title for an elderly woman. Indeed, the Super Mario RPG: Legend of the Seven Stars Nintendo Player's Guide simply refers to this character as the "chambermaid".