Frankie Stein is a 2010-introduced and all-around character. She is a simulacrum, specifically the daughter of Frankenstein's monster and his bride, and a student at Monster High. Having been born as a 15-year old only recently, Frankie may have the intelligence and physical capabilities of her born-age, but she does not have the appropriate life-experience. She has been rapidly gaining ground, though, mostly with the support of the close group of friends she created around herself. In everyday life, Frankie has an unrelenting positive disposition, which allows her to easily make friends and motivates her to always look for solutions that help out as many people as possible, but it also makes her prone to being taken advantage of. It doesn't help that she is a tad clumsy either. Befitting her heritage, Frankie has an interest in broad range of scientific subjects and she favors the practical side over the theoretical one. This interest extends to sewing and cooking, both skills she excels at and has utilized to create other simulacrums.
In Latin American Spanish, when the series was dubbed in Colombia, she was voiced by Nathalia Gutierrez in volume 1 and 2, now, when the series began to be dubbed in Mexico, she is voiced by Karla Falcón since volume 3.
Frankie is friendly, sweet, and polite with a clumsy streak. She is the most naive of all the ghouls; being so young, she tries to learn all she can about the world through monster teen magazines, although their advice often cause awkward moments for her. She is charismatic and outgoing, causing many ghouls to like her.
Despite setbacks, she remains upbeat, hopeful and determined to find her place within Monster High. Frankie can also be insecure and react too quickly, such as instantly labeling Abbey Bominable as rude, and accusing one of her friends of being the Ghostly Gossip.
Despite being only a few days old, Frankie's physical age is that of a fully-grown girl in her late teens. Also, despite been a monster made up of parts from different people, she has been created with a well-balanced, attractive body, unlike her father.
She has long white hair with black streaks, similar to her mother's hair, which may be inspired by the Bride of Frankenstein (see Classic Monster). It was originally styled with jagged streaks, and her fringe was pulled back over her head and pinned back with a hairclip, but was later changed in the book series so the streaks where more straight and natural-looking, and is now styled with a side fringe that covered her forehead, again held with a clip.
She has light, mint green skin, and has a condition known as heterochromia which gives her odd-coloured eyes - one green, one blue (though likely from being assembled from multiple bodies, rather than genetics).
Frankie has visible stitches all over her body, most obviously near the joints of her limbs, around her neck, and across her right cheek. She also has two bolts fixed into her neck, which allow her to absorb electricity to use as energy to keep her body working. Her neck bolts flash like a light bulb when she has an idea.
There are several plot-holes concerning Frankie's age in the series. If the webisodes follow the same timeline as the "New Ghoul @ School" special, she would have started school when she was 8 days old or younger. In "Party Planners", she turns 16 days old. For her to be consistently 16 days old, most of what happens in the webisodes would have had to have happened in the same day, although this can't be, as in "Frightday the 13th" she stayed overnight, which means she is a day older than what she is now.
Over the course of the first book series Frankie's over a year old. Her SDCCI 2010 diary describes her first day alive, while the regular diaries start on the day she has just turned 16 days.
In the cartoon series, due to having pass yearly events, it is implied that she is over a year old by now. Meanwhile, on the back of Frankie's Picture Day box, her age is listed as "How many days has it been now?".
Without knowing it, Frankie is an icredibly powerfull monster, at young age. Though most of her powers are to do with electricity, from her lab heritage, she has a wide range of other abilities, most of them still fresh.
- Electrokinesis: Frankie can create and control electricity, either accidently or on purpose. Through her bolts, when she gets emotive, or through her body, mostly through her hands, Frankie can charge anything or shock anyone. She herself can be charged too, either by the Recharge Chamber from "Freaky Fusion" or simply by random flashes of electricity and lightning bolts.
- Magnetism: In "Bad Scare Day", it is shown that, when her two bolts are switched from one side to the other, reversing her polarity, Frankie can attrack objects with magnetic proportions.
- Pyrokinesis: Frankie can create fire at times too, mostly due to her electrokinesis. She can do this by beaming electricity at flammable materials or by simply rubbing her hands.
- Chronokinesis: In "Boo Year's Eve", Frankie was able to stop time accidently, but then rewind certain people's actions, confirming then Frankie's ability to control time. Why she would have such power is unknown.
- Body Separation: Frankie can detach certain parts of her body and control them at distance, which she frequently does with her hand to reach tight places.
- Sewing: Due to being a monster made of various detached body parts only connected by stiches and strings, Frankie has developed a skill on sewing and tailoring, which is not only one of her favourite hobbies, but it comes in handy in times when her body is dismantled too.
- Life Creation: Like her father and grandfather, Frankie has been shown to creating life herself, such as Hoodude and the gingerbread boy.
Frankie lives with both of her parents, named Viveka and Viktor Stein in the first book series, in "a house that looks like a cross between a Swiss chalet and a research lab" in the monster side of New Salem in the United States of America. Her parents moved there from, presumably, Germany many years before her creation. Both her parents are multi-disciplinary scientists and college professors, though her mother is not as obsessed over science as her father. Because the Steins waited for over a century before they considered themselves capable of giving a child a steady home, despite their strong wish for one, they dote on Frankie and do everything they can to keep her happy and safe.
Taking after her parents in the science department but not so much the responsibility department, Frankie has already created two other simulacrums herself: Hoodude Voodoo and gingerbread boy. As the former's surname suggests, they aren't considered part of the Stein Family, but the Steins have taken responsibility for them. At least in regards to Hoodude, it has been arranged that he gets to live at Kindergrubber's and it seems the Steins keep paying for his education and other needs.
Frankie also has one Uncle Egor, presumably the man who assisted her grandfather in creating her parents. Contact with him is good and he's the kind of man anyone can rely on.
Frankie is best friends with Draculaura, Clawdeen Wolf, Lagoona Blue, Abbey Bominable, Cleo de Nile, Deuce Gorgon Jackson Jekyll and Holt Hyde. She has no monsters she considers enemies, even trusting manipulative characters like Toralei Stripe and Cleo without question.
Frankie's pet is a dog hybrid named Watzit which her father constructed from the parts of other animals.
In the Monster High books and TV specials, Frankie has five pet lab rats whom she calls the Glitterati; their names are Gwen, Gaga, Green Day, Girlicious and Ghost Face. They also appeared in "New Ghoul @ School" and "Fright On!".
In "New Ghoul @ School", Frankie had a crush on Deuce Gorgon. This caused issues when she lied and told Deuce's real girlfriend, Cleo, that she was dating him. Cleo became very upset, thinking that Deuce had cheated on her, but the issue was later resolved when Frankie came forward with the truth and surprised Cleo with a Justin Biter concert.
In "HooDoo You Like?" Frankie was concerned about being left out of the group for not having a boyfriend, and decided to make one for herself, creating Hoodude Voodoo. The ghouls explained that they would always be friends with her regardless of whether or not she had a boyfriend, and Frankie admitted that she didn't think that she was ready for boys just yet.
In the webisode "Miss Infearmation" Frankie develops a crush on Jackson Jekyll after saving him from being bullied by Manny Taur, and invites Jackson to come to Cleo's tomb party with her. She is upset when he doesn't show up in "Hyde and Shriek", because he had turned into Holt Hyde before entering the party.
She soon forms a crush on Holt, blushing at the nicknames that he gives her ("Frankie 'Fine' Stein", "High-Powered Hottie") and dances with him on the DJ deck in "Hyde and Shriek". This forms a love triangle between her, Jackson and Holt. After introducing the two to each other via video recording in "Dueling Personality", she realized she couldn't choose and "hit the pause button" on their relationships.
In the Monster High book series she has a crush on Brett Redding (a monster mad normie) with a very protective girlfriend, Bekka Madden. At the september semi he mistakes Frankie for Bekka and kisses her; causing her head to be ripped off. She briefly dated Billy Phaidin, after his friend Candace Carver gave him a makeover so he wouldn't be invisible and could woo Frankie. Frankie and Billy went to a Lady Gaga concert together, but after kissing and needing to rush home due to Billy's makeup melting and wanting to make it in time for Clawdeen's party, the two realize that neither one felt "sparks". Frankie then gets back together with Brett, because her feelings for him are stronger. Brett chose Frankie over Bekka.
- October 23, 2007: Mattel requests the trademark for Frankie Stein.
- May 05, 2010: The Monster High website goes live, featuring Frankie Stein's profile.
- May 05, 2010: Frankie Stein's profile art is revealed.
- May 05, 2010: Frankie Stein makes her animated debut in the Higher Deaducation commercial.
- May 05, 2010: Frankie Stein makes her 2D cartoon debut in "Jaundice Brothers".
- Early July, 2010: Frankie Stein's debut doll is released as part of the 'Basic' series.
- Early July, 2010: Frankie Stein makes her diary debut in her 'Basic' diary.
- Early July, 2010: Frankie Stein's debut plushie is released as part of the Friends series.
- September 01, 2010: Frankie Stein makes her Monster High book debut in Monster High.
- February 12, 2012: Frankie Stein makes her 3D cartoon debut in "Why Do Ghouls Fall in Love?".
- September 05, 2012: Frankie Stein makes her Ghoulfriends book debut in Ghoulfriends Forever.
- October 22, 2014: Frankie Stein makes her anime debut in "Monster High Life Is Amazing!".
- Mattel's director for global brand marketing, PJ Lewis, stated that "Frankie’s head mold it is a bit more square than the rest, as Frankenstein is known for having a square shape to his head."