I have an interesting theory about how the Monster High and Ever After High worlds are parallel universes and how certain things have crossed over similar to the Equestria Girls universe's Mirror. C.A. Cupid proved the two worlds are connected by using a mirror to cross over. My theory starts with Gigi and the Grimm brothers. Genies originated in the Ever After High universe and one of the brothers influenced one of the finders of the lamp to create Wisp so Gigi wouldn't be lonely while waiting for a new master. At some point the sisters from the lost Two Sisters fairy tale got a hold of Gigi's lamp and to escape the destiny written for them, they used their one of their wishes to escape to another world and the mirror Cupid used was created and the sisters ran into the portal carrying the lamp. Doing so also created other portals that are well hidden. One of them is at the bottom of the deep end of the pool. No one knows what's down there so it lies undiscovered. The sisters managed to fit into the Normie population since they were humans to begin with and lived the rest of their lives happily in their new home while their story in the Ever After High world disappeared. They kept a journal of their new life and the history behind Gigi's origins which they gave to the Genie as a thank you gift after using their final gift. This is the book Clawdeen found while banished inside the lamp during 13 Wishes. Occasionally other objects suddenly appear in the MH world which is why during the attic scene in 13 Wishes we see some stuff that belong to EAH characters such as Briar's rose or Raven's crown. My theory is that the catacombs is also a hiding place for another portal that connects to the EAH world by means of a labirynth under their school. And this is how the scrapped cross over movie would have occurred. What do you guys think of my theory.