Francis "Frankie" Foster is the caretaker at her grandmother's home for imaginary friends. She is voiced by voice-acting/singing veteran, Grey DeLisle.
Frankie Foster is based on creator's Craig McCracken's wife Lauren Faust. She is the beautiful, caring, friendly, hard-working, sweet, capable, easygoing but still short-tempered granddaughter of Madame Foster. According to her driver's license, she was born on July 25, 1984, is 5'8" ft tall, and weighs 127 pounds and has green eyes ("Bus the Two of Us" - picture shown below Infobox, and "Destination Imagination" - one of her eyes peeks through a window of the Foster's model). However, in The Trouble With Scribbles, Mr. Herriman said she had let the scribbles out in autumn of 1984 and she appears to be 2-4 years old in the flashback (or at least where she's old enough to talk).
Frankie has apparently lived at Foster's nearly her entire life, having moved there in her early childhood. It is unclear what happened to her parents, though Frankie mentions during "Who Let the Dogs In?" that they helped her conquer her fear of ghosts when she was a child.
As she grew into her teenage years, Frankie, who had spent her life in the company of imaginary friends, soon took on the role of taking care of pretty much everything at Foster's. She was placed in charge of cooking, cleaning the house, doing the laundry, running fund raisers, driving the house residents around in the multicolored bus, and otherwise taking care of her grandmother's foster friends in most ways. She occasionally shows signs of stress as a result of her many duties, though its primary source seems to be Herriman's constant over-enforcing of the house rules and that he forever expects her to work harder, despite her already full workload.
She also knows about Mr. Herriman's fear of dogs as shown in "Who Let The Dogs In?" when a couple with a lost stray dog comes in and Mr. Herriman is sent into a panic, but Frankie saves him by making the couple and their dog leave and explaining that Foster's isn't an animal shelter. Mr. Herriman is still traumatized and nervous, as he knows "Dogs eat rabbits."
Still, despite all her work, she does manage to keep a social life, and is even allowed to go on the occasional date (assuming Mr. Herriman doesn't keep her working late with more chores). She is also often swayed by Bloo's "get rich quick schemes" and has proven to be an efficient ally in promoting Bloo's agendas when she feels she can get a good profit or outcome out of it.
She is a fan of punk rock, as discovered in "Everyone Knows It's Bendy" and "Imposter's Home for Um… Make 'Em Up Pals." She is also proficient in web-design, creating and maintaining the Foster's web-page (as seen in "World Wide Wabbit").
According to concept art, Frankie was originally intended to be much younger, a teenager, and much more into punk rock than she already has been shown to be. Many drawings depicted her being always angry. While her looks have changed, she always had the same shirt (depicting a stylized version of The Powerpuff Girls, another Craig McCracken creation), green zip-up, hooded sweatshirt jacket, and ponytail.
Although she is generally an in-charge, no-nonsense sort of girl, Frankie can be quite charming, as seen in "Frankie, My Dear," where Mac, Bloo, an imaginary Prince Charming, and a pizza delivery boy named Chris all develop a crush on her, and in "Good Wilt Hunting," where two nerds (Douglas and Adam) consider her to be a vision of beauty. Frankie can be skeptical at times, as seen in "Imposter's Home for Um... Make 'Em Up Pals," where she thinks Goofball John McGee isn't an imaginary friend because of his overly-human appearance. She also has an unhealthy addiction to Madame Foster's home-baked cookies, occasionally indulging in a feeding frenzy, first buying $1200 worth, and then $2400 (20 and 40 dozen respectively). In addition, she may have a case of road rage, especially seen in "Good Wilt Hunting," where officer Nina Valarosa, Eduardo's creator, hands out tickets for various traffic violations. She also won the election for president of the house in "Setting A President," but resigned when she found out the pay was worse than her old job (and because Mr. Herriman was devastated without his old job).
Frankie also gets extremely stressed out in "Cheese A Go-Go." She has to deal with picking up imaginary friends, run errands and a lawsuit between her grandmother and Jackie Khones over a tuna sandwich. She also has problems with Cheese and the others throughout, which becomes worse when Bloo uses an observatory public address system to tell everyone (including her) that Cheese is an outer-space alien and in essence invites the creatures from other worlds to pick him up. The stressing out was also a central point on the movie Destination Imagination, where she escaped to a world to be pampered by a character named World, a face that could move around onto anything.
Frankie's character design appears to be loosely based on that of Lauren Faust, the show's supervising producer (and real-life spouse of series creator Craig McCracken). Oddly enough, Frankie, unlike her grandmother, seems to have never created an imaginary friend of her own; most likely this is because she grew up surrounded by them. However, she is most likely to have adopted World.
Her favorite TV show is a soap opera called "The Loved and the Loveless," which is very popular among the house residents.
In FusionFall, she's found standing outside the Foster's Gate. She is worried about Coco running off (a reference to the episode "Mondo Coco," when Coco goes through various misadventures and comes in contact with various obstacles when somebody leaves the door to Foster's open. At the end of the episode, Frankie yells, "Who left the door open!? Who knows what would happen to Coco if she got out?!") and Mac going to find her, but she expects them to be at the KND Jungle Outpost. Nearby the house, Mandark, has started a construction of an Imaginasium so he can better study Imaginary Friends. Frankie has gotten into arguments with him about the designs. Eddy secretly has a crush on her, and only mentions it in one of the Imaginary Reinforcements mission parts. She gave her hair clip to the KND and Urban Ranger's scientists for nano development.