Brain Tank

The Courier's brain, known in-game as the Brain Tank, is the disembodied, isolated, conscious, and interactive brain of the Courier.

Background
The Courier's brain is removed by the Think Tank of the Big Empty and subsequently forgotten about. Soon after, Dr. Mobius takes the opportunity to seize the brain and secretly take it away to his stronghold, the Forbidden Zone, as leverage against the Think Tank. The brain enjoys the peace and quiet of its new home, along with the relative safety and cleanliness, when compared to the wasteland in the Courier's head.

Quests

 * Old World Blues: Get your brain back!

Appearances
The Brain Tank appears only in the Fallout: New Vegas add-on Old World Blues.

Behind the scenes
Sunil Malhotra, the brain's voice actor, stated that his performance was an homage to Stewie Griffin from Family Guy, and that "Stewie basically lives in MY brain, so naturally..."

Bugs

 * After progressing through the dialogue with the Brain Tank, the option to say "So, what, you'd rather just stay here? Never leaving that tank of... whatever that stuff is?" appears, however, if you choose it, you will get stuck in a never-ending speech loop. This also occurs on PC as well, specifically at the moment when the brain begins reminiscing about past feats by Courier. In the observed case, the loop occurred between the brain recalling Jason Bright's departure and the activation of HELIOS One.
 * Workaround: to get out of dialogue loop, in the console, type (close all menus). This will exit the current dialogue with the Brain Tank, and allow the player to walk away or enter dialogue again, but the loop will occur once more if the same response is selected, so choose wisely.
 * The trigger to this bug is the line about Jason Bright. If the Courier does not complete Come Fly With Me prior to speaking with the brain, this bug will not occur.
 * This bug is still present in PC v140525.
 * Reloading the game from a previous save is the best way to fix this on console.