Derpy Hooves, the fan-favorite pegasus with crazy eyes, can be seen briefly at 04:43 in the Applebuck gala fantasy, at 06:45 in the Twilight Sparkle gala fantasy, as well as on a date with a pony at 13:11.
This episode is a pony-fied take on the musical 'Into The Woods', a play about classic fairy tales that go wrong (ie Cinderella goes to the ball and marries her Prince Charming, but he cheats on her with the baker's wife). The mane 6 all have wishes for what will happen at the GGG, but they all don't go as they hoped. Additionally, the song 'At the Gala' is an homage to 'Prologue', the opening number of 'Into the Woods'.
Friendship Report: The ponies learned that some things don't go the way they thought, but friends can help make them even better.
Twilight turning an apple into a carriage and mice into horses is reminiscent of the fairy tale Cinderella. Rarity also loses one of her slippers on the stairs like Cinderella does.
The ponies wear the dresses Rarity designed for them in "Suited for Success".