Monster High is a fairly harmless mini media empire designed to sell dolls and such to young tweens and teens. It's no worse than My Little Pony and it's good to keep that in mind while watching something like "Ghouls Rule."
The idea is simple, in a world with monsters being somewhat common they have to go to school like normal people. Like normal people all the cliques and stereotypes we are familiar with from high school are evident. There are the popular girls, the nerdy girls, the catty want to be popular girls, and you get the idea. The plot of this little special is that it is Halloween which is now a time the monsters fear as it is the time where the "normies" go monster hunting crazy. There is a rising hostility between the normal high school and monster high. In this mess is Frankie Fine who is trying to find the true spirit of Halloween, Holt who is half normie and feeling heat from both sides, and Cleo who is being pushed by her daddy to take charge of the situation any way she can.
All in all it's a normal halloween special for kids. I liked some of the characters, but no one really rang my bell. Not surprising again the demographics are squarely aimed at teen girls which explained the endless shots of high heeled "monster" shoes.