–Mr. Herriman calling Frankie
Frances "Frankie" Foster is Madame Foster's 22-year-old granddaughter and the all-purpose caretaker at Foster's. She cooks, cleans, buys groceries, drives the transport bus and is basically in charge of tending to the physical and emotional needs of the house's many imaginary friends. A spunky and compassionate girl -- albeit sometimes overwhelmed by her job and certain troublemaking residents and the uptightness of Mr. Herriman -- she is friends with most of the imaginary friends at Foster's (particularly Wilt, Eduardo, Coco, Bloo and the eight-year-old boy Mac, and also Goo) and can be described as a protective big sister to them.
In the Future, Frankie is nowhere to be found. This implies that she might have fallen along with most of the Imaginary Friends and the Home, or that she had managed to escape Foster's and fallen on her way to Sector V.
The PastIn the Past, 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 Part 2 of the Imaginary Reinforcements mission line. She gave her hair clip to the KND and Urban Ranger's scientists for Nano development.
- The design on Frankie's T-shirt is actually the Powerpuff Girls; upon closer inspection, they are actually silhouettes of the girls, each one in their respective color. This would make sense, as both shows were created by Craig McCracken.
- Fusion Frankie's eyes are red in her render art, but yellow in-game. She is not the only fusion with this discrepency.
- She is voiced by Grey DeLisle, who also voiced Mandy.
- As of July 22nd 2019, Frankie received a new character texture in Retro Beta Patch 2.9
- As of August 21st 2019, Frankie received a new character texture, scale, and slight model difference in Retro Beta Patch 2.11