The series follows the main "ghoulfriends" (girlfriends) of the franchise such as Frankie Stein, Clawdeen Wolf, Draculaura, Lagoona Blue, Cleo de Nile, Ghoulia Yelps, and Abbey Bominable; and how they manage in the "Monster High" high school. Other characters appear throughout the series, such as the antagonist Toralei Stripe (a were-cat).
This tv show contains 2 potentially triggering events.
In volume 3 episode 8, The Nine Lives of Toralei, Toralei is shown as a kitten, abandoned in a cardboard box along with her siblings. She much more closely resembles a real cat here.
Not against real-world minorities, however in volume 1, episode 24, Hatch Me If You Can, the teacher Mr. Rottington insists that all sea monsters are horrible parents, mirroring some real-world racial prejudices. He is shown to be in the wrong for this.
In terms of Gen 1 MH, Jinafire Long, the only prominent Asian character, has yellow skin. The Japanese vampires in the "Sayonara Draculaura" webtoon have pale yellow skin. Also in G1, Isi Dawndancer is a Pochahontas level of Indigenous representation, and Marisol Coxi's name and design is based on the Maricoxi people of Brazil who were infamously compared to monkeys. Most of these issues are recitified in G3 (Jinafire, for example, is no longer yellow)
Throughout multiple episodes in Volume 4, Jane Boolittle is shown watching and eavesdropping on people from the ventilation system because she's too shy to talk to people directly - as a result she learns personal information about people without their knowledge. Spectra Vondergeist also commonly watches people without their knowledge throughout the series in order to collect gossip for her blog.
In Volume 2 episode 28, Hiss-teria, Deuce reveals that he once accidentally froze his childhood pet dragon, Smokey, into a stone statue due to having poor control over his gorgon powers. While it's stated that Smokey isn't dead and will eventually be reanimated, he has been stuck there for many years and is never shown being brought back in the series, effectively making it a death.
Teenager but I guess it kinda counts. According to official lore Spectra has been said to not have been born a ghost and that all she remembers from her death is that it was tragic.
Somewhat. An earlier episode has Frankie freaking out over acne and trying to get rid of it. This is portrayed as a good thing, despite the franchise's message hinting otherwise.
On two separate occasions a male character is made to disguise himself as a female character as a joke - In volume 1 episode 27, Parent-Creature Conference, Slo Mo is forced to pretend to be a female relative of Lagoona's in order to attend a parent-teacher conference instead of Lagoona's actual parents. In volume 4 episode 13, Master of Hiss-guise, Clawd is forced to dress up as Elissabat to make a distraction so the real Elissabat can escape.
Not in the series proper, but don't be surprised if you catch any G1 purists or transphobes maliciously misgendering G3 Frankie (G1 Frankie used she/her, G3 Frankie uses they/them)