This was technically in the simple PMV folder, but I think it does a bit more than that. No one has really shown Twilight's growth with such impact. From our perspective as a fandom, we've only seen a very small fraction of her life, and only her Ponyville years at that.
She spent every waking moment trying to improve herself and reach the same level as Celestia in magic proficiency. This was shown pretty clearly in The Cutie Mark Chronicles, when she first views the raising of the sun. If glimpses at her past were any indication, pre-ponyville years were completely dominated by study and advancement in her attempts at reaching that level. She just needed that extra push of social skills to hit the alicorn level. I'd assume a princess would need to be able to attend to her subjects without pulling up a manual. Maybe that is the real reason for friendship being the final requirement?
Anyway, get the video below the break!
