Again with the Doctor Who soundtrack...
But I got it in my head that Discord is the greatest villain the ponies have faced, so using the music used to introduce the Doctor's greatest enemy seemed appropriate. In the end, really, this actually turned out as a little episode summary, music+the main points of the episode.
--------------------------------------------------------------------------------­­
My Little Pony: Friendship is Magic is © Hasbro, all art/writing is © to their respective artists.
All The Strange Strange Creatures performed by the BBC National Orchestra of Wales, © Independent Online Distribution Alliance

Video is legal under fair use:

~FAIR USE~ Copyright Disclaimer Under Section 107 of the Copyright Act 1976, allowance is made for "fair use" for purposes such as criticism, comment, news reporting, teaching, scholarship, and research. Fair use is a use permitted by copyright statute that might otherwise be infringing. Non-profit, educational or personal use tips the balance in favor of fair use.