EarthBound Halloween Hack

EarthBound Halloween Hack is a ROM hack of the Super Nintendo Entertainment System video game EarthBound, developed by American indie developer Toby Fox. Gameplay takes much of the same as in the original EarthBound, featuring many role-playing game elements. It takes place in an alternative timeline of EarthBound where Varik, the main character, soon enters the lab of Dr. Andonuts, who has been wracked with grief under the assumption that his actions during EarthBound's story killed his son Jeff and his friends.

EarthBound Halloween Hack has been described as a "prototype" of Fox's 2015 game, Undertale, featuring similarities in themes and writing. It was one of Fox's earliest experiences in game development involved using RPG Maker with his three brothers to make role-playing games and creating ROM hacks in high school. The hack draws inspiration from the Brandish series, directly using its main character Varik as a substitute for EarthBound's Ness and its final boss track, "Megalovania", being inspired by the Brandish 2: The Planet Buster song "Gadobadorrer".

EarthBound Halloween Hack was release in October 2008 for a ROM-hacking competition on the EarthBound-centered forum Starmen. It received generally mixed reception by journalists, praising its mechanics and overall writing while criticizing the edgy humor. The track "Megalovania" was later remixed for subsequent projects Fox worked on, including Undertale. The track would become widely popular, which spawned various memes and remixes to the degree of being named its own subgenre on YouTube. The creator Toby Fox looks back on the EarthBound Halloween Hack poorly, calling it a "bad rom hack with swears".