The "alter egos" can easily be explained by the fact that between the Liverpool and Pepperland is the Sea of Time. The Beatles even see alters of themselves while sailing through it!
Pepperland is at the bottom of the sea... which is full of salt.
The Vacuum Monster is shown walking into the Sea of Monsters from the far horizon, which is completely empty. Given what it's shownto becapable of, just how many monsters were consumed before the Beatles showed up?
