Frankie is Taylor's eccentric younger sister and the younger daughter of Michelle Hathaway. She doesn't seem to be scared by Louie, Ray, or Miles, unlike her older sister. She particularly likes things that are spooky, like Louie's headless boy trick and the dead bird on their piano. She seems to like Louie, and thinks he's awesome.
- She owns mannequin heads.
- Her favorite mannequin head is named Big Gurt.
- She is on the school volleyball team, though she makes excuses to get out of practice.
- She's a straight A student.
- She knows The Thundermans have superpowers.
- She had a keyboard named Kevin, until it was maliciously destroyed.
- It is revealed in "Haunted Surprise" that her favorite foods are: Sloppy Joe, Corn on the Cob, Steak, and Lobster.