Nothin' But a Hound Dog

 is a quest in Fallout: New Vegas.

Quick walkthrough

 * Talk to the King in Freeside at the King's School of Impersonation
 * Talk to Julie Farkas about what can be done to help Rex.
 * Return to the King with the news that Rex can be healed.
 * Take Rex to Doctor Henry in Jacobstown to learn how he can be fixed.
 * Acquire a new brain for Rex from one of these optional sources:
 * Rey's Brain increase Rex's attack.
 * (Optional) Acquire a new brain for Rex from one of Old Lady Gibson's dogs.
 * Violetta's Brain increases Rex's movement speed.
 * (Optional) Search for an exceptional canine brain among the Fiends.
 * Lupa's Brain increase Rex's HP from 450 to 550.
 * (Optional) Search for an exceptional canine brain among Caesar's Legion.


 * Occasionally NCR Guard Dogs will drop their brains, which can be transplanted into Rex for no benefit.
 * Return to Jacobstown and have Rex's brain transplant performed.

Detailed Walkthrough
Talk to King in Freeside. Ask him about Rex and he will tell you that something is wrong with him. He will then ask you to go to Julie Farkas. She will tell you that there is a man, Dr. Henry, in Jacobstown who can help. You must then tell King that Rex can be fixed, having him allow you to take Rex to Dr. Henry. He will tell you to to find at least one dog brain to fix Rex. The first brain is at Old Lady Gibson's scrapyard, just north of Novac. She will ask you for 700 caps, if your barter skill is at 70, it will be less. The second brain is at a Fiend camp near Vault 3, there are two sections to the camp, one is a type of kitchen with Cook-Cook as the leader, in the other section of the camp is a structure built from ruined campers (trailers), this section is populated by Fiend Guard Dogs, Violetta, a boss Guard Dog and a hound master called Violet, you can acquire Violet's mangled head or Violet's Head if you do not damage it. You can acquire Violetta's brain after killing her.

The third is in The Fort, which you gain access in Render Unto Caesar quest. Talk to Antony about Lupa and eventually about a brain for Rex. Antony will then ask you to give Lupa an honorable death. You must fight Lupa in the arena with only a Machete (Fallout: New Vegas) and no armor. Your reward will be Lupa's Brain if you defeat her in a battle.

Choosing to implant Rey's brain will give Rex a perk to increase his attack damage. Choosing to implant Violetta's brain will give Rex a perk to increase his speed. Choosing to implant Lupa's brain will give Rex a perk to increase his Damage Threshold.

It should be noted that you can only choose one.

Bugs

 * If you succeeded in killing Rey and getting Rey's Brain for free, talking to Lady Gibson afterwards will still offer you the option to purchase the brain for 700 caps or barter for a lesser price.


 * Transplanting Lupa's brain to Rex may result in Rex's HP being set at 100/0 and no way to increase his health with stimpaks. (PC,360)


 * Kings' Gambit and G.I. Blues can interfere with this quest, making it impossible to finish. If you go back to King after talking to Julie Farkas and he says something like "My eyes on the street tell me you haven't spoken to our mutual friend Orris yet, until you do, we got nothin' to talk about", it means that the G.I. Blues quest is still considered active. You can still talk to Orris and hire him as a bodyguard, but you will not be able to finish G.I. Blues, making it impossible enter dialog with the King.


 * If you collect more than one brain, the extras will stay in your inventory as unremovable quest items.


 * If you have Lupa's Brain in your inventory twice, it will not appear as an option for transplantation.


 * If you tell Rex to go back to the Lucky 38 and then go to the Fort to get Lupa's brain, talking to the Legionary Trainer next to the drawbridge in the Fort can make Rex's Search and Mark Perk Lost message appear again, saying that Rex has gone to the Lucky 38, and the player will get stuck, unable to perform any actions. The only known fixes for this are to load a previous save, or restart the system.


 * Old Lady Gibson may spawn at Helios One hostile. If you don't scavenge Rey's brain its body will actually stay out back in the solar field.

Behind the Scenes

 * This quest is a reference to the Elvis song of the same name.
 * Hound Dog is an original song by Big Mama Thornton and Elvis Presley was one of many who covered it. Not that this is even remotely relevant or adds anything.