Wasn't sure where to put this, or even if I should at all, since this may be old news.
Anyway, this may require some explaining.
A "Niconico Douga Medley" is a long medley of many various anime and game music, invented by the users of Niconico Douga, a popular Japanese video streaming site.
"Automated Mario" is a custom-made Super Mario World level that requires no input from the player. Our plucky plumber is sent through the stage by the level itself.
Put them together and you get...