When Princess Celestia comes down with a mysterious illness, Sunset takes it upon herself and Twilight to get to the bottom of it, which would be hard enough if she wasn't dating the other Twilight in secret.
At the changelings Masquerade Ball, Starlight has to face her feelings and figure out the identity of another - all while transformed into a great and powerful friend. Who is the other pony and why did they pick Starlight as their disguise?