Mrs. Fitzgerald is a minor character in The Amazing World of Gumball, and is the mother of Penny. She is introduced in the episode "The Date," where she gets upset when Gumball destroys her younger daughter's memorial picture of Mr. Cuddles.
Mrs. Fitzgerald is presumably a shape-shifting rainbow fairy like her daughter Penny, but she is taller, has smaller antlers, has an hourglass figure like her other daughter and Penny, and we have not seen her in her fairy form, unlike Penny, of which we see in the episode, "The Shell." She also wears light brown and white cowgirl boots, suggesting she may be from the heartland.
Not much is known about her personality. However, she seems to be extremely generous, as she was willing to give Gumball and Darwin large amounts of money, her boots, her ring and even her kidney when she felt they needed help, as seen in "The Gripes."