A self-styled inventor, 24-year-old Moira grew up with an uncommon curiosity about the world in the trading community of Canterbury Commons. Sometime before 2263, she moved to Megaton.  She's read almost every book that's come through the town. Although her reading has taught her a wide variety of useful knowledge, she has nearly no actual experience with the world, so she doesn't always understand how it can be applied outside of her workshop. After a recent accident with a domesticated centaur, Moira was inspired to write a book to help others survive in the wasteland and avoid similar dangers.
After the guide was completed (with the help of the Lone Wanderer), it became considerably popular, managing to reach places like the distant Mojave Wasteland in less than four years.
By 2297, she continued to run the Craterside Supply, and ran the distribution network of the survival guide. On September 10, she began work on a biography of the Lone Wanderer.
Moira is the owner of Craterside Supply. She spends the day sweeping and trading as well as conducting odd experiments. She opens the store at 8:00 a.m. and closes at 8:00 p.m. The Megaton Craterside Supply store is also her home. She sleeps upstairs and if the Lone Wanderer is caught trespassing after hours she will become increasingly upset. The only time she will leave her shop is if Megaton is destroyed in the quest The Power of the Atom. If the Wasteland Survival Guide quest is completed before Megaton is destroyed, she will instead stay near the entrance to the ruins, and only be able to repair, lacking an option to buy or sell items.
If the Lone Wanderer blows up Megaton, she will not die; instead she will become ghoulified. If the Wasteland Survival Guide quest is started, or she is met to receive an armored Vault jumpsuit, the Wanderer will have to visit the Megaton Ruins to find her. If the quest was not started, she can be found in the Underworld, whereupon she will claim she was 'out-of-town' during the detonation, and apparently unaware of her recent affliction. Depending on how the Wanderer breaks the news to her, she will either fall into despair or remain positive.
Convincing her that writing The Wasteland Survival Guide is a bad idea will result in a 30% discount on her wares and increase her Repair skill from 24 to 54 (72% condition). Karma will also be lost but grant the Dream Crusher perk. This will also make her considerably less positive and more gloomy.
Moira's voice does not change after becoming ghoulified.
If the Lone Wanderer decides to blow up Megaton, Moira will not fast travel to Underworld, but instead walk there directly. This makes it extremely likely for her to be killed on the trip there; this is due to a combination of several threats on the way, a less-than-straightforward route, and Moira's observed unwillingness to defend herself.
Even though Carol in Underworld says it takes months or years to become ghoulified, Moira will instantly become a ghoul if Megaton is destroyed.
If her terminal is hacked, her current experiments can be tracked.
Upon Megaton's destruction, and encountering Moira after she becomes a ghoul, the Lone Wanderer can tell her "Don't take this the wrong way, but you got ugly real fast." This is a reference to Army of Darkness.
The script notes imply that Moira Brown was previously called Lea Marsh.
pcps3xbox360 Occasionally, Moira will not move from the Megaton ruins after the town has been destroyed if you have completed the quest Wasteland Survival Guide. She will stand in front of Megaton and can only repair. This will happen also if you complete the quest by depressing her. She will only say usual things like "Oh good. Someone who doesn't have a brahmin to wash up. That's a nice change." [verified]
pcps3 Even when Moira is dead, opening her Craterside Supplies container, and stealing an item, she replies "Hey, that's valuable junk!", despite being dead. [verified]
ps3xbox360 In a very rare occasion if you save, kill Moira, and reload the save she will not be there and therefore rendered completely lost. [verified]
ps3 In a very rare occasion when Moira dies from an explosive or the Bloody Mess perk would find (if afterwards detonated the atom bomb) Moira Brown floating outside Megaton in her 'corpse' pieces and any interaction with the Lone Wanderer is ignored. [verified]
pcps3xbox360 Attempting to trade with Moira Brown after she closes Craterside Supply each night results in her saying she's closed for the night. However, if told "I'm looking to buy some things for my house," and then "Okay, let me take a look at your stuff," she can be traded with as if her store was open. [verified]