Frankie Stein is daughter of Frankenstein's Monster and his bride. She has waist-length black and white hair and has heterochromia (Her right eye is blue, her left one is green). Frankie's fashion sense revolves mostly around blue plaid prints and schoolgirl style. She is 15 days old. In "Miss Infearmation", Frankie has developed a crush on Jackson, unconcerned that he is a normie. However, in the next episode "Hyde and Shriek", she is blushing near Holt, unaware that he and Jackson are one and the same. After the stress both Holt and Jackson were placing on her when they learned their identities, Frankie has placed her relationship with both on pause. Her latest diary mentions a gargoyle football player known as "7" (his jersey number) with a Scottish accent. Her pet is named Watzit, who is put together from several different animals, but most resembles a domesticated dog. She is voiced by Kate Higgins.
Draculaura is the daughter of Count Dracula. She is 1,599 years old with black and pink hair. Draculaura does not drink blood and, in fact, faints at the mere mention of the word. She is a vegan vampire who abstains from drinking any kind of blood and eating meat. Draculaura's taste in fashion is influenced by the Japanese Lolita style, and is typically in shades of pink and black. She has had many crushes in the short while the franchise has been out, but her current boyfriend is Clawd Wolf, Clawdeen's older brother. She is a member of the Fearleading Squad with Frankie and Cleo. She has a pet bat named Count Fabulous. Draculaura is voiced by Debi Derryberry.
Clawdeen is the daughter of the Werewolf. She is 15 years old and comes from a rather large family. Clawdeen complains about Howleen, her younger sister, whom she shares a bunk bed with. Howleen is constantly chewing on Clawdeen's shoes and borrowing her clothes and getting them dirty. Clawdeen is considered the fashionista of the group who loves leopard print and open-toed pumps. Because her hair grows unnaturally quickly, she is constantly having to shave her legs. Clawdeen dreams of owning her own fashion design brand, plays on the soccer team, and, in the webisodes, enjoys track and field. Clawdeen does not like Cleo, because Clawdeen incorrectly thought that Cleo two-timed Clawd with Deuce Gorgon. After Clawd explains to Clawdeen that his breakup with Cleo was, in fact, mutual, Clawdeen and Cleo become frenemies. In the doll diaries, Clawdeen seems to not be fond of the idea of Draculaura and Clawd dating, but in the webisodes, she eventually warms to the idea. She has a purple pet cat named Crescent. She is voiced by Salli Saffioti.
Lagoona Blue is the daughter of a Sea Monster and an ocean nymph, making her the first known mixed monster. Lagoona loves to surf and is so skilled at it that she can do so in her platform sandals.Her skin tends to dry out if she spends too much out of the water. She is 15 years old and has blonde hair with blue streaks, thanks to the chlorine in the school pool. Lagoona is a transfer student at Monster High from down under the sea and captain of the Surf/Swim team. She tends to dress casually most of the time, but will dress up for special occasions. Lagoona is dating Gil, a freshwater member of the swim team, but because Lagoona is saltwater, Gil's parents disapprove of the relationship. She has a pet pink piranha named Neptuna. She is voiced by Laura Bailey.
Cleo de Nile is the daughter of the Mummy. She is 5,842 years old. Her clothing motif typically involves wrappings and streaks of real gold in her hair. In the first season was the main antagonist, but in the second season became one of the protagonists. She took over as fearleading captain when her older sister, Nefera, graduated. Cleo works hard on getting out of her sister's shadow. Cleo has a very bad relationship with her older sister Nefera, because Nefera always rub Cleo her superiority in all. Cleo is considered stuck up, but will always help her friends if they need it. Throughout the franchise, Cleo has been softening towards the other girls and slowly losing her princess ego, but she still remains a self-centered. She has a turquoise pet cobra named Hissette and can even talk to snakes and get them to do what she says. However, Cleo refuses to manipulate her boyfriend, Deuce, with this ability. In the book, her full name is Cleopatra. She is voiced by Salli Saffioti.
Ghoulia is the daughter of a zombie couple. Ghoulia is 16 in monster years and has a pet baby-blue owl named Sir Hoots-A-Lot. She is the smartest ghoul at Monster High. Ghoulia is a shy and bookish girl, but her best friend, Cleo de Nile, refuses to let Ghoulia be the wallflower at a party. Ghoulia's social life has improved greatly since befriending Cleo. Ghoulia's romantic interest is with Sloe-Moe, a tall, male zombie on the Chess team. Ghoulia is well-known to be a hardcore fan of "Dead Fast," an in-universe comic book series. She is voiced by a producer of the Monster High webisodes, Audu Paden. Her normie name is Julia Phelps.
Deuce is the son of the gorgon, Medusa. Like his mother, he has snakes for hair, which he styles in a "snakehawk." He is 16 years old and hopes to get his driver's license soon. A member of the casketball team, Deuce loves to cook and is quite a skilled chef, but he is too self-conscious to showcase his culinary prowess to anyone. Deuce inherited his mother's ability to turn people into stone, though he has been able to control the effect so that it lasts for only about 24 hours. In "Hiss-teria", he reveals that petrified his first pet, a dragon named Smokey, when he was a young boy and the effect has lingered to the present day. Deuce is dating Cleo, who seems to always find new ways for him to spend all his money on her. Despite that, Deuce genuinely loves Cleo and wrote a song to express his feelings for her. His pet is a two-tailed rat which he named Perseus, after someone Medusa clashed with in her past. Understandably, Medusa is not amused. He is voiced by Yuri Lowenthal.