Greg Vegas has heard about a world about ponies living together. Now it's his intention to go to this world and see it for himself. However his two sons would also meanwhile develop an interest of going to this world, but not only to see it, but to take over it.
Later, Twilight and her friends would stumble upon these three bad humans. After learning that they're trying to take over Equestria, it is there time to stop them.
Only, how can you when they have already done it?