The Internet is perhaps the greatest creative force at has ever existed. Nothing proves that more than the energy behind fandom communities. People focus their dedication to a piece of art and use that energy to expand on the property in ways the original creators never dreamed.
Of course, this isn't new. Building on top of previous art has been a staple of the creative process for as long as humans have created art. Now, however, the process by which something is imitated, parodied, or built upon had been shrunk to almost zero.
So, of course, let's take a look at My Little Pony. As they have been doing since the show began they took an existing piece of art and parodied it for use on the show. This time they picked a famous song from the music man which had been famously parodied in the Simpsons. So while the source is the same for the secondary work created by two separate professional animation teams the Internet combined the parodies to create a third level of parody. A parody within a parody, if you will. Best yet this came out only hours after that episode of My Little Pony had aired.
"The Super Speedy Cider Squeezy 6000" from My Little Pony: Friendship is Magic
"Monorail" from The Simpsons