The premise for Welcome to Monster High actually contradicts a lot facts stated in previous monster high movies and webisodes. The original webisodes "New Ghoul @ School" shows Frankie entering an already established Monster High and meeting the other ghouls once there rather than being part of the school's construction. Freaky Fusion also puts the school at around 200 years old, having been established in 1814, much earlier than the events that take place in Welcome to Monster High.
A new animation style is used for this movie. This means that the Monster High movie series has used three animation styles so far.