What if, instead of creating her own friendship magic to solve the problem of Starswirl the Bearded's unfinished spell, Twilight took the easy way out and just kept casting it until the ponies' cutie marks were on the right way round again? Well I guess Princess Celestia would be all like "TWILIGHT I AM DISAPPOINT". 'Cause that's kinda the magic equivalent of "solving" a Rubik's Cube by taking it apart with a prybar and reassembling it.
(Actually, the episode implies that the spell mixes the Elements of Harmony randomly instead of just cycling them, and there's actually a 119-to-1 chance against the spell actually putting them all the right way round at any time, but I ignored that because that would make the cartoon waaaaaaay too long!)
EDIT: Hiya, Equestria Daily!
EDIT 2: For the record, I loved "Magical Mystery Cure", and no I don't seriously think Twilight should have done what she does in this cartoon. It's just a joke, people. :}
EDIT 3: That means I DON'T wanna hear about how you thought the episode should have gone this way because it would be sooo much better than that dumb ol' "Twilight gets to grow awesome wings" ending. Keep it to yourself!