PC It is possible to stealthily kill Lupa and loot Lupa's brain from her corpse. If she is successfully killed without the player being noticed, Antony may not "notice" that Lupa has died and will still give you the option to fight her in the arena for her brain. If the player accepts, it is possible to obtain a second Lupa's brain, but having two of the brains in your inventory will cause Dr. Henry to not recognize that you have the brain at all, making it impossible to give Rex Lupa's brain. To solve this, either revert to an earlier save, or enter player.removeitem 0013d851 1 in the console. Make sure that you only have one instance of Lupa's brain.
PC There is a chance, if you finish the quest by talking to Calamity rather than Henry, that the variable for Rex's brain won't be set in the quest, you'll get the ending for if you hadn't actually transplanted the brain at all. Use the following command to fix this set "001176B8".nTransplantResult to X
X is one of the following:
0 for no transplant ending.
1 for Rey's brain ending.
2 for Violetta's brain ending.
3 for Lupa's brain ending.
Xbox 360 If you have already killed Old Lady Gibson as well as her dogs, Rey's quest marker may change positions on the world map either showing up at Novac or Gibson Scrap Yard. In both cases, Rey's corpse may be stuck inside the ground, making it hard for the player to see Rey's body or even realize that the body is glitched.
Xbox 360 Upon transplanting Lupa's brain Rex's hitpoints may become set at 100/0 making him impossible to heal.
If the player implants Rex with Lupa's brain, prompting Boone to initiate the dialog in which he leaves the Courier, the game will sometimes glitch upon leaving this conversation. The result is that Boone will no longer be accompanying the player, but will still follow the player wherever they go, and (upon gaining close proximity) greeting them with his standard welcome, "Is it time?" There are, however, no dialog options available, effectively breaking Boone as a companion.