Mrs. Fairywinkle is the mother of Wanda and Blonda, the wife of Big Daddy, the maternal grandmother of Poof and Cosmo's mother-in-law. Her name is unknown, although there are many possible suggestions (such as Big Mama, Big Mommy, and Mama Fairywinkle)
She has never made an appearance in the show, nor has her name been revealed, but she was mentioned in Blondas Have More Fun! by Wanda, who said to Blonda: "Mom always liked you best!". She is possibly divorced from Big Daddy, as in the episode Big Wanda, he is shown living alone and entering in a relationship with Mama Cosma.
She was mentioned another time in "A Fairly Odd Christmas", when Cosmo said "I never been that scared since Wanda's mother moved in" (meaning she moved into the castle in Timmy's fishbowl). She might also be very ugly since Cosmo said that he hasn't been scared since Wanda's mother moved in. Her ugliness could also be the reason why Wanda's parents got divorced in the first place, and had to temporarily move in with Cosmo and Wanda since she would have nowhere else to go. It could also be possible that they got divorced since Big Daddy is a Mafia Boss.