The cartoon continuity is one of the three main Monster High continuities, told through the weekly-to-biweekly webisodes and occasional TV specials that make up the Monster High cartoon series. The cartoon continuity lightly overlaps with the diary continuity, in that most storyline events are either confirmed to happen in both or implied to happen in both. However, those events do not occur in exactly the same way or in exactly the same order between the continuities, which causes them to be separate continuities.
The webisodes are divided in volumes, and the cartoon continuity's storytelling angle differs per volume. Volume 1 focusses on elaborating on the main cast, though does so haphazardly with no consideration for order or plot. A few webisodes and character traits tie into each other, but coherency is not Volume 1's forte. Instead, it opts for a gag-per-webisode format and utilizes characters as the joke needs. Volume 1 also sees the gradual introduction of a few characters, but none of them get more than at most three near-inconsequential appearances.
Volume 2, in contrast, is story-heavy, with an ongoing plot focussed on the failures and successes of the Fear Squad. Some webisodes do end on a gag, but most on a cliffhanger or a feel-good-feel. Time plays a role in Volume 2, with summer vacation occurring half-way through. More characters are elaborated on, and new ones are introduced mostly in plot-related ways.
Volume 3 blends the properties of Volume 1 and Volume 2, returning to the gag-per-webisode format but being far more consistent in character portrayal than Volume 1. Volume 3 also brings back several character traits that Volume 2 ignores while maintaining Volume 2's character development. The way new characters are introduced depends on the character - some lean towards Volume 1 treatment, some to Volume 2 treatment.
The TV specials flow along with the Volume they belong to. The Volume 1 special is an alternative telling of the Volume 1 webisodes, or at least its first half. The Volume 2 special is continuity-heavy and firmly takes place at the end of Volume 2. The four Volume 3 specials match the Volume 3 webisodes in continuity, but it's difficult to say when they occur relative to them. Also, no Volume 3 special-originated character has appeared in the webisodes thus far.
Years and dates are rarely mentioned in the cartoon series. Therefore, a timeline is at best estimated based on the assumption that Volume 1 and Volume 3 webisodes occur in the order they aired in unless proven otherwise and the assumption that the Monster High schoolyears have the same setup as real-life schoolyears.
A noteworthy 'but' in understanding the cartoon continuity is that there are at least three Volume 1 continuities in existence. They are best explained by looking at the roster of the Fear Squad. In the webisodes, Lagoona and Draculaura are members of the team, or at least enough to talk of the team as "we" and decide that Frankie gets to be fearleader. Frankie joins the team by accidentally performing several impressive moves while chasing her hand. In the TV special, Draculaura and Clawdeen are members of the team. Frankie joins by showing she can remember a routine and not being afraid to try, though she ends up on probation after hurting Cleo's feelings. Volume 2 does not favor either of these continuities and continues on a hypothetical continuity in which Frankie is member-on-probation, none of her friends are or have been fearleaders, and Toralei, Meowlody, and Purrsephone have always been on the team.
That said, the Volume 1 special may only be an alternative to the first half of Volume 1, meaning an alternative to the webisodes "Jaundice Brothers" up to "Totally Busted". The rest of the Volume 1 webisodes could follow from the TV special.
The Kind Campaign webisode "Kind: The Shockumentary" is assumed to be part of the cartoon continuity. If so, despite being released during Volume 2, the presence of a werewolf introduced in the Volume 2 special places the cartoon continuity-wise in Volume 3. The exclusive doll-related webisodes "Zom-Beach Party" and "Fashion Emergency" are marked as part of Volume 3, but make more sense to take place during Volume 2 and perhaps even Volume 1.
The cartoon continuity changes angles and content often with little explanation, perhaps as a result of having to work a story into just a few minutes. Regardless, this has made the cartoon continuity one of the least coherent.
- Frankie Stein's age in "Jaundice Brothers" was fifteen days. She became sixteen days old in "Party Planners", and said her age was sixteen days old in "Shock and Awesome". These are respectively webisode 1, 5, and 18, and few webisodes could take place on the same day. Nor is it likely that "Party Planners" and "Shock and Awesome" are to be placed right after (the first half of) "Jaundice Brothers". By Volume 2, Frankie's age stops being brought up in detail. However, her age still occasionally brings up disconnect, such as how Halloween in "Ghouls Rule" is Frankie's first halloween despite at least a year having passed since her creation.
- Shortly after enrolling at Monster High, Frankie gets her friends to join in making a recording to get the Jaundice Brothers to play at their homecoming dance.
- Cleo tries to make Clawdeen lose a talent show, but ends up making her win.
- Due to agility and a misunderstanding, Frankie becomes a member of the Fear Squad. Lagoona and Draculaura may also be members at this point.
- With Bloodgood ill, Lou Zarr takes over Trigular Calcometry 101. A confrontation with Deuce ends in his petrification and cancellation of that day's class.
- Frankie turns 16 days old and Draculaura 16 centuries. Their friends throw them a surprise party.
- Lagoona has been desiring after Gil for a time and more or less due to her friends' intervention, Gil asks her for a date.
- Clawdeen did not study for her SAT and tries to get the answers from Ghoulia. Ghoulia thwarts her attempt.
- Draculaura has been desiring after the new boy at school, Heath Burns, for a time. Cleo accidentally gets Heath to notice Draculaura.
- Frankie accidentally reverses her polarity, causing her to become magnetic and her charge to zap out randomly. Ghoulia fixes the situation.
- The girls try to escape Coach Igor during Study Howl, because he'd make them run laps, which would ruin their looks for picture day. However, the exercise they get from escaping ruins their looks anyway.
- Ghoulia has been desiring after Slo Mo for a time and thanks to her friends gains the courage to talk to him. Slo Mo reciprocates.
- Frankie acquires a pimple from cursed sugar eyeballs. With some Fearasil, Ghoulia helps her out.
- Clawdeen and Cleo sabotage each other's attempts to land the role of leading lady in the Hamlet schoolplay. Draculaura eventually gets the role.
- Lagoona can't bear to let frogs be dissected for Mad Science class any longer and saves them. The frogs take up residence in and around the school.
- Cleo and Frankie break a statue belonging to the school and are called to Bloodgood's office. Cleo puts the blame solely on Frankie and before Frankie can protest, she's the hero of the school for breaking the statue and freeing a teacher who was trapped inside.
- It is both Friday the 13th and Halloween - a double bad luck day until the clock hits three o'clock and the day qualifies as over. Using a protective charm of the De Nile family, Ghoulia goes to the clock in the main hall and adjusts it forward by six hours.
- Cleo has stolen Ghoulia's science project, but Lagoona and Frankie help her get payback.
- Frankie has yet to see her first movie and her friends set out to make the experience perfect for her. Frankie ends up not seeing any movie because she has to provide the electricity so the others can watch.
- Draculaura is asked to turn into a bat, which she can't but won't admit. She falls asleep in the belfry while trying to change and an actual bat flies down into the school building, where it is mistaken for Draculaura.
- Cleo spreads a rumor about Clawdeen to keep her from running for Scream Queen. Clawdeen wasn't running in the first place, and Cleo's rumor becomes so mangled by the people that send it through that it ends up getting Clawdeen elected.
- Heath Burns makes the mistake of challenging Clawdeen to two laps around the track while there's a full moon that night.
- Based on her horoscope, Draculaura thinks she has found her ideal boyfriend. Her friends help get them together.
- Cleo uses a De Nile idol to get all kinds of benefits for a day, ignoring her father's warning that it is cursed. Once the day is over, the idol steals her hair as payment.
- Lagoona and Gil get to take care of a gargoyle egg for a day as a Mad Science assignment. They handle the egg perfectly and get to see it hatch by the end of the week.
- Ghoulia tries to further her relationship with Slo Mo, but is too shy. Frankie helps her overcome her nervosity and connect with Slo Mo.
- During a sleepover at the Wolf residence, Frankie is subjected to "Truth or Scare". Challenged to announce a party at "her" house by Cleo, Frankie ends up announcing a party at Cleo's house.
- Lagoona's relatives are invited for a parent-teacher conference and Lagoona thinks this means she turned in a bad essay. Her friends dress up Slo Mo as a family member of Lagoona's and send him to the conference instead. It turns out the conference was called because Lagoona is the class's best student and has written a perfect essay.
- On Monday, Frankie experiences her first day at Monster High. She has trouble feeling welcomed.
- On Tuesday, Frankie socializes with Clawdeen and Draculaura but makes an enemy out of Cleo. She believes she can do better and resolves to try out for several clubs to increase her social circle.
- On Wednesday, Frankie finds her attempts to join school clubs one failure after another. Her last chance is the Fear Squad, which coincidentally is looking for a new member. Frankie gives an impressive performance, but accidentally humiliates Cleo, the captain. She ends up meeting Lagoona and Deuce, the latter she develops feelings towards, and is restored in her confidence when Draculaura and Clawdeen tell her that Cleo wants to interview to see if she's worthy of becoming a fearleader regardless of the accident.
- On Thursday, Frankie decides to fake herself and imagine to be accepted by Cleo. This works well until she is asked if she has a boyfriend. Due to coincidental events, Frankie replies that Deuce is her boyfriend. Cleo reveals that Deuce is her boyfriend and accuses him of cheating on her. As Frankie realizes her mistake, she finds herself abandoned by all the friends and potential friends she has made so far.
- On Friday, Frankie decides to amend for all the pain she has caused. She apologizes to all her friends, but arranges something special for Cleo. With her friends' help, she explains Cleo that she lied about Deuce and get the two together again. Furthermore, she reveals to Cleo that she arranged a special concert by her favorite singer just for her. Cleo is impressed and forgives Frankie and even makes her a member of the Fear Squad, if on probation. Frankie is just happy to finally have obtained some good friends.
- - During fearleading tryouts, Frankie accidentally humiliated Cleo, the captain, but she was still made a member, though one on probation.
- Toralei Stripe and Meowlody and Purrsephone were members of the Fear Squad long before Frankie joined.
- None of Frankie's friends bar Cleo were on the Fear Squad prior to Frankie.