Anon spent the last year in Equestria, learning about its rights and rules, along with the new laws of physics which would be considered a joke back on earth. One of them goes as follows: "Every creature within Equestria's borders is affected by musical magic, making them sing when dealing with intense emotions."
That night, as he was making his way to his home through the streets of Ponyville, he thought back to his home. To his family, his old life, and his old hobbies. He reminded himself of one of the old cartoons he used to watch as a kid, Sesame Street, specificaly to one song he remembered: "I dont want to live on the moon."
https://www.youtube.com/watch?v=kIq8jLj5TzU
He heard the instruments start playing in the background, and he already knew what awaited him.
Unbeknown to him, Princess Luna was passing by, and decided to listen to what the popular human had to sing about.