Old World Blues

Old World Blues is the third add-on for Fallout: New Vegas, developed by Obsidian Entertainment and published by Bethesda Softworks.

Synopsis
In Old World Blues, the Courier is abducted by the Think Tank, a group of pre-War scientists that have replaced their bodies with machines. Learning that the Think Tank has removed and subsequently lost the Courier's brain, the Courier aids the Think Tank scientists in fighting Dr. Mobius, the rogue scientist currently in possession of their missing brain. Exploring the Big MT facility, the Courier rediscovers lost technology and fights off lobotomites, robo-scorpions, and more.

Finally meeting Dr. Mobius, the Courier learns that he is not actually evil, but has messed with the Think Tank's memories and constantly threatens them in order to keep them from experimenting on the entire wasteland. By stealing the Courier's brain, Dr. Mobius was preventing the Think Tank from using the brain's unique properties to move their own brains into host bodies and escape the crater. After choosing what to do with Mobius and reacquiring their brain, the Courier returns to the Think Tank and can choose to either convince them to stay in Big MT or to kill them.

Factions

 * Think Tank
 * The Circle

Weapon mods

 * K9000 mod - Mentat chow
 * K9000 mod - Resla roil
 * LAER mod - auxiliary recharger chip
 * LAER mod - prismatic lens

Quests
The experience points that are rewarded for quests are based on the player character's level upon the quest's completion. The total experience points available for the main storyline quests is anywhere between 3,000 (for levels 1-4) to 22,000 (for levels 45-50). The experience points gained from the side quests range from 75 to 500 per quest.

Behind the scenes

 * The Big Empty was a location that was scrapped from Black Isle's canceled Fallout 3 (Van Buren).
 * At some point, Chris Avellone set his location on his Twitter profile to Big MT, Mojave, placing the Big Empty as a location within the Mojave Wasteland and thus teasing its possible appearance in a future Fallout: New Vegas add-on. Since then, Avellone has also changed his Twitter avatar.
 * According to Chris Avellone, Old World Blues was to feature invented "zero-versions" of Power Armor, such as Power Arms, Power Chassis, and other items, but the idea was cut.
 * The add-on is a homage to the science fiction B-movies of the 1950s. There are many references to these types of movies throughout the add-on, and both Dr. Mobius and Dr. 0 mention them directly.
 * Old World Blues was nominated for Best DLC Award at the 2011 Spike Video Game Awards. It was the only one of the Fallout: New Vegas add-ons to be nominated.
 * The add-on's main quest shares many similarities with the 1939 film The Wizard of Oz in that the Courier searches for their brain (Scarecrow), their heart (The Tin Man) and their spine (courage for the Lion) after initially being unconscious after entering Big Mountain (as Dorothy was knocked unconscious in order to enter Oz). Additionally, Dr. Mobius is initially portrayed to be malevolent or sinister, much like the Wizard of Oz himself, only to have it revealed that he is quite misunderstood. The Big Mountain Transportalponder! acts as the Ruby Slippers, taking the Courier back home. Dr. Mobius mentions this subtly, though he refers to the three main characters of the film as a "band of murderous thugs."
 * Several concepts from Old World Blues such as the proton axe and the robo-scorpion are inspired by Wasteland, the 1980s game which is considered to be Fallout's predecessor.