The US prototype of Mother has some enemies that are edited to remove knives, blood, smoking, and shiny breasts for censorship reasons.

In the English prototype of Mother, some of the characters were redesigned, possibly to avoid resembling characters from Charles Schulz's Peanuts comic strip. One NPC character was given pigtails to reduce her resemblance to Marcy, Peppermint Patty's best friend, and the dust cloud was removed from an NPC that looked like "Pigpen". Ninten's mom was also given a different hairstyle, possibly because it resembled Sally Brown, Charlie Brown's sister. Ironically, Ninten's shirt was given a stripe, which made him look similar to Charlie Brown.

If the player walks through the tunnel leading to Reindeer prior to actually taking the train, they will find a pile of bones. If the player talks to it, it'll say "Get on the train, or you will have a hard time like me."

There is a secret message in the game from Shigesato Itoi. While in Yucca Desert, there is a spot on the map which, when talked to, will say, "Yucca Desert is the most boring part of this game. Keep this place to yourself, please. signed... Shigesato Itoi"

Itoi has said that the difficulty of Mt. Itoi was due to his attitude towards the end of development. During the fine tuning phase of development, when it came to Mt. Itoi, he had enough.

According to Phil Sandhop, the script writer for the unpublished English release of Mother, the process of localizing the game motivated Nintendo to design games with an international audience in mind, to minimize localization efforts in the future.

The version of Mother included in the Japanese-only compilation Mother 1+2 for the Game Boy Advance is actually the unreleased U.S prototype translated back into Japanese.

There are 5 Prototype NES Cartridges of the North America version of Mother/Earthbound.
4 prototype cartridges were owned by collectors, and the fifth was owned by Nintendo of America Inc.

The English translation was complete, but it was never released in North America until 25 years later.
On June 14 at Nintendo World Championships 2015 Nintendo announced Mother was coming to the Wii U Virtual Console, under the title "EarthBound Beginnings".

The NES prototype of Mother has an anti-piracy message, preventing it from being played on an emulator.

A ROM-translating group, "Neo Demiforce", created a ROM that circumvents the anti-piracy measures. They also added the word "Zero" to the title screen in order to prevent confusion with Mother 2, released in North America as Earthbound for SNES.

Most of the game's locations were renamed for American audiences, as some of the cities were named after holidays or had religious references.

•Mother's Day was renamed Podunk.
•Thanksgiving was renamed Merrysville.
•Santa Claus Station was renamed Union Station.
•Halloween was renamed Spookane.
•Easter was renamed Youngtown.
•The Advent Desert was renamed the Yucca Desert.
•Valentine was renamed Ellay.
•Holy Loly Mountain was renamed Mt. Itoi.

In a 1997 interview with game's composer Keiichi Suzuki published in the GSLA, he stated that originally his goal for the game was to write pop music. It was a request from Shigesato Itoi, who wanted Suzuki to make pop music with real vocals, and then use instrumental versions of those songs in the game:

Contrary to popular belief, The Legend of Zelda franchise is not the first appearance of the ocarina instrument in a Nintendo franchise. The ocarina first appeared in Mother as the Ocarina of Hope. It’s appearance in the official Mother strategy guide resembles a transverse ocarina, similar to their appearance in the Zelda games.

In a 2019 interview with Game Center CX host Arino Kacho, director and series creator Shigesato Itoi revealed that Ninten's asthma was inspired by his own experiences with the disease. According to Itoi, he would often play video games late at night while trying to fall asleep sitting up, as lying down would induce severe coughing fits. This resulted in him developing an interest in making a game with Nintendo, to whom he felt "indebted" for keeping him busy during a difficult part of his routine. Once development on Mother started, Ninten's asthma was one of the first traits that Itoi came up with. Itoi stated: