In an Interview with Shigeru Miyamoto about Mother 2 (known as EarthBound in America), he admitted that Mother 2 was the first RPG he beat:

EarthBound's Official Strategy Guide contains pictures of real locations. This may be to give the guide a more realistic feel, as if it wasn't a guide. The strategy guide also includes newspaper articles, which mainly revolve around Ness and his party's journey.

There is a section where Ness will enter his own subconscious. In this segment, the North American version of the game has Ness wearing his Pajamas, but in the Japanese version, Ness is more or less naked, wearing nothing but his hat.

In Mother 2 (the Japanese version of EarthBound), the cultists of Happy Happyism appear with the letters HH on their forehead (for Happy Happyism). In EarthBound, a pom pom was added and the HH was removed, presumably to try to make the cultists look less like members of the Klu Klux Klan. Also, possibly because HH on an already Klan-like sprite could be construed to mean "Heil Hitler". The city "Threek" was renamed "Threed" in EarthBound. Like the cultists, this may also be to avoid any link to the Klan, as Threek could be seen as Three K's, or KKK.

The main antagonist of EarthBound, an alien known as "Giygas", was made by Shigesato Itoi and described as "a living being that deserves love." While the character first debuted with a different design as the final boss of Mother, Giygas' appearance in EarthBound was inspired by a childhood incident where Itoi accidentally walked into the wrong movie at a theatre and watched the 1957 Japanese horror film "Kenpei to Barabara Shibijin". Itoi was traumatized by the film, where he confused a lovemaking scene that ends in murder as a rape scene. He says it had a "sense of terror having atrocity and eroticism side-by-side, and that's what Giygas's lines at the end are":