Francis "Frankie" Foster is the love interest of Mac from Fosters Home for Imaginary Friends. She is voiced by Grey Griffin.
She is the 22-year old granddaughter of Madame Foster and is also the caregiver of the house. She is a kind-hearted and attractive young woman, but has a temper when pushed enough, especially when given orders from Mr. Herriman. Even though Frankie's the one who basically runs the house, she still has to answer to Mr. Herriman. Frankie also has a friendly-rivalry with Mac's imaginary friend, Bloo.
Mac has first shown interest in her when she gave him a kiss on the cheek when he helped her with some paperwork, but she wasn't having romantic feelings for him. In "Ticket to Rod", it is revealed that Mac still has a crush on Frankie as he still has feelings for her as he goes on a date with Frankie. Frankie is also like a big sister to Mac.
- Age: 22
- Hair Color: Red
- Eye Color: Green
- Height: 5'9"
- Weight: 127 lb (57 kg)
- Clothing: Green Hoodie Jacket, White T-shirt with outlines of the Powerpuff Girls, Purple Skirt, Orange/Yellow socks, Blue sneakers, and Pierced ears
- Formal Clothing: Black Dress, Black Choker, Large Gold Hoop Earrings, Four Gold Bracelets, Pantyhose, Black High Heels, Bun Made Hair
- Other Clothing: Pink and Purple Party Outfit