Gosh knows why Twilight Sparkle wants to go back to the Mirror World. They better have a good excuse for that. Unless it’s Flash Sentry, then HEY-YO. NO EXPLANATION NECESSARY.
Sunset Shimmer is back from rehab, and apparently friends with the Main Six. A bunch of new tramps are here to mesmerise Canterlot High after being expelled from Monster High by entering the Battle of the Bands.
Not to be outwitted, the Main Six form their own band. Sunset Shimmer tries to fit in after being rejected by the Monster High tramps at her own audition and plays with the Main Six.
They discover Sunset Shimmer plays surprisingly well for a girl in a leather vest (she still has it on? C’mon…) and is soon coaxed by the rivalling antagonist band like Rainbow Dash and the Wonderbolts to join theirs.
Sunset Shimmer eventually does and suddenly plays against the Main Six, only to discover the meaning of Friendship and LOYALTY (RAINBOW Rocks) and regrets her betrayal of the Main Six, before switching bands and rocking hard for the Main Six just enough to win the competition.
The awesomeness of their music shatters the glowing necklaces on the rival band, knocking them out of the trance. They are sorry.
Yay. Hugs all around. Twilight kisses Flash. Roll credits.