Nanny Num Nums/ Nanny McFear is Rosebud's evil, youth-stealing grandma who appeared in the episode Nanny Num Nums (Nanny McFear).
She appears to be a nice grandma at first and she constantly speaks in rhymes. However, once she gains your trust, she will suck out your youth and energy.
*Her name 'Nanny McFear' is a parody of the character from the show with the same name: Nanny McPhee
*Her black umbrella could be a reference to Mary Poppins