Cartoon Network Halloween Movie

Hello everyone! Sorry if my english is not the best but i have talked to a few friends and no one seems to remember this movie.

It was usually streamed during halloween times in South and Central america during what i could say between 2009 - 2016, but if it rings any bells please let me know.

It was a school of monsters where the main characters were children representations of Dracula (wearing braces and having a bratty or entitled personality) a mummy (Skittish and shy) and finally a werewolf (Non verbal and wild)

The models of the characters had small bodies and big heads, i remember an specific scene of the mummy being trapped inside a staircase, the door closing behind him.

I remember the color setting being from colorless to black and white, and the animation style as i remember it were more solid colors than textures!

Thank you for reading and if you try to find it, good luck!