Once upon a time, there was a human male named Brian.

Brian, in his cosplay costume of his video game hero, Mario, bought an item from somebody named The Merchant at his local gaming convention and wound up in Equestria as a result of magical spells and some other shit.

The Mane Six killed him immediately upon his arrival. They were fed up of having humans in costumes coming into their world.

The End.

Author's Note

And the Mane Six lived happily ever after. At least until the next displaced fanfic drops another annoying human in a cosplay suit...