While all the students of Canterlot High are going about doing their business, Rainbow Dash stumbles upon a huge discovery, the portal to Equestria is currently active! While all the girls are gathering after RD's call two of them are taking a bit longer to show up. While waiting for Pinkie Pie and Sunset Shimmer Rainbow Dash demonstrates to the rest of the girls that the portal is in fact active, this is the time Pinkie chooses to arrive in the most amazing way possible, a tackle-hug meant for the whole group.

With one last: PINKIE! they are off.

Waking up someplace else, as their pony self on the other side, namely Equestria! But even now things seem to go wrong, for they all have not one, but two new additions to their group. As well as having the portal closing on them!

Without their possible guide in the form of Sunset Shimmer who never made it in time; What are the girls to do? And what about their new 'friends'?

Set just about after the "Rainbow rocks" Movie. Also, have you seen the "secret" scene after the credits? If not You should, It's kind of a spoiler but It will make all of it easier to understand.