Mysterious - Mario Paint

"Mysterious - Mario Paint" is a high quality rip of "Mysterious" from Mario Paint.

Joke
This is the song "Happy H. Christmas" by Maniacs of Noise, remade using the instruments on mariopaintcomposer.net, an online version of the music mode on the original game.

It's also a reference to the video, it is a mystery, hence the name of the song, Mysterious.