The Vault - Fallout Wiki

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For other characters of the same name, see Rex (disambiguation).
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Nothin' but a hound dog
Biography and appearance
AffiliationDenver City Police Department (formerly)
Caesar (formerly)
The King
5 of Spades
LocationThe King's School of Impersonation
Dialogue FileRex's dialogue
Mentioned inOld World Blues
QuestsNothin' But a Hound Dog
You'll Know It When It Happens
SPECIALStrength: 6
Perception: 8
Endurance: 8
Charisma: 4
Intelligence: 2
Agility: 8
Luck: 5
Derived StatsDT: 10
Health: 176 → 484
Attack Damage: 40 → 100
PerksSearch and Mark
Companion Suite (When in party)
Level8 → 22
Base ID00118e71Ref ID0010d8df
Gametitle-FNV.pngGametitle-FNV OWB.png
Gametitle-FNV.pngGametitle-FNV OWB.png

Second, he doesn't like hats, or the people wearing them. Don't ask, I don't know. Maybe because it rhymes with rats.

The King on Rex

Mk. III Cyberhound, LEO Support Model, Serial no. B955883, known to the people of Freeside as Rex (King in Latin), is a cyberdog in Fallout: New Vegas under the ownership of the King. He is suffering from neural degeneration as a result of his aging brain.[1]


Part German Shepherd, Rex is a "Cyber-Hound Mk III L.E.O. (Law Enforcement Officer) Support Model" that has been around since pre-War times. He was born as a regular dog in 2072[2] and served in the Denver City Police Department. Sometime before the war, he was cybernetically enhanced and turned into a cyberdog - serial no. B955883, although the circumstances of his cybernetic alterations remain unknown. He survived the destruction of Denver and the harsh wastelands, eventually becoming Caesar's companion for a time, but was lost in battle, specifically being blown up in the First Battle of Hoover Dam.[3][4] He later reached Freeside, where he came under the ownership of the King, who loves him dearly. Rex does not like rats, or hats, according to the King. The King says his dislike of hats may come from the fact that hat rhymes with rat.[5]

In recent years, Rex's brain has been degenerating and Rex has been slowly dying. The King has contacted the Followers of the Apocalypse, seeing if they can help Rex but they do not have the capabilities to perform brain surgery nor the knowledge of cybernetics that is needed. However, the Followers do know that a Doctor Henry in Jacobstown has these expertise and is likely Rex's best hope.[6]

Interactions with the player character

Interactions overview

Perk nociception regulator.png
This character is essential. Essential characters cannot be killed.
This character is a permanent party member. They grant the Search and Mark perk.
Perk empathy synthesizer.png
This character is involved in quests.


Other interactions

  • Should the player have a hat equipped when first talking to Rex, he will start barking at the player because of his hatred for hats, but ease Rex by telling him they're both on the same side.
  • If player has Rex as a companion and goes to recruit Arcade Gannon, Arcade will say "A courier, a doctor, and a cybernetic dog. Maybe when this is over we can open an act at The Tops".
  • If the player has the Wild Wasteland trait, Rex will say "aroo" to the courier at a random time. The Courier can then ask if Jimmy has fallen down a well (this is random and does not always happen). This adds the location Jimmy's well to your map. Down in the well you will be confronted by a mole rat, and there will be a skeleton. Next to him is the Abilene Kid LE BB gun, 2 tins of BB's, a super stimpak and a rawhide cowboy hat. This is a reference to the television series Lassie, as well as to the quest with Laddie in Fallout 2.

Non-player character comments

  • Nightkin: Head voices speak of doggy with squishy brain.
  • NCR civilians: What on earth is *that* creature?
  • Gun Runners: I've never a dog like that. Who thinks up these things?
  • Boomers: That thing is housebroken, right?
  • Legion: The dog is part-machine... but its brain is flesh.
  • Brotherhood of Steel: What a fascinating animal. I'm sure the scribes will want to take a look at him.
  • Brotherhood Scribe: Is that a Mk. III Support Model you have with you? I've seen references to them, but never with my own eyes. I imagine he makes a great pet.
  • Powder Gangers: Didn't know they still had robo-dogs around.
  • Great Khans: A robot dog? Never seen one of those before.
  • Followers: Look at that - a cyber-dog. There can't be many of those left.
  • Freesiders: Good to see Rex still around and kicking.
  • The Kings: Hey, isn't that the King's dog?; Heya Rex, how you doing boy?
  • Strip Securitrons: Be advised, visitors will be held responsible for the behavior of any robots accompanying them.
  • Omertas: I think there is something wrong with that dog.
  • Outer Vegas denizens: What the hell? Is that a half-robot dog?


The following section is transcluded from Fallout: New Vegas endings. To modify, please edit the source page.
# Image Transcript Requirements
1 Rex end slide 01.png He had survived police service in Colorado, the Great War, combat duty with the Legion, and being the companion of The King. But, in the end, Rex finally succumbed to the horrors of the wasteland.
  • Rex dead.
2 Rex end slide 01.png Having never received a replacement brain, Rex finally succumbed to old age, abruptly shutting down forever one quiet morning. After two centuries of life and decades of service to humanity, Rex collapses and dies.
3 Rex end slide 02.png Revitalized by Violetta's brain, Rex eventually learned to balance the memories of his old life with Violetta's experiences among the brutal Fiends. His mind had difficulty adjusting, but Rex eventually found peace with his new, more vicious self.
  • Complete Nothin' But a Hound Dog by using Violetta's brain.
4 Rex end slide 03.png With the transplant of Lupa's brain, Rex gained all of the donor's experiences traveling with the Legion. These melded well with his own memories of the Legion, and his new mind quickly adjusted to the myriad memories.
  • Complete Nothin' But a Hound Dog by using Lupa's brain.
5 Rex end slide 01.png After Rey's brain was transplanted into Rex's cybernetic body, it took Rex some time to adjust to the old scrapyard dog's memories. Eventually, Rex's mind settled peacefully, melding his own memories with that of long travels with Old Lady Gibson.
  • Complete Nothin' But a Hound Dog by using Rey's brain.

If Old World Blues is installed, and Roxie has been created, it triggers set of endings which add a bit more to Rex's story.

The following section is transcluded from Old World Blues endings. To modify, please edit the source page.
# Slide Voice-over narration In-game condition

2 Fnvdlc03 endingslide roxie.png There, she ran across Rex at the Kings School of Impersonation. His brain was failing. That was all right, he was still smarter than the Think Tank. The two of them constructed a litter of cyberpups, a small army of Boston terrifiers that gnawed and devoured anything in their path. Rex is alive, but not obtained as a companion
2 Fnvdlc03 endingslide roxie.png There, she ran across Rex, who had been following the Courier, just as she had. They barked for a while, and realized they had a lot in common. The two of them constructed a litter of cyberpups, a small army of Boston terrifiers that gnawed and devoured anything in their path. Rex is alive and a companion on standby
2 Fnvdlc03 endingslide roxie.png There, she ran across the corpse of Rex. She dragged him back to the Big Empty and had him rebuilt for company. The two of them constructed a litter of cyberpups, a small army of Boston terrifiers that gnawed and devoured anything in their path. Rex is dead


Icon armored vault suit.png
Assault carbine icon.png
Icon briefcase.png
Carried items
Icon male severed head.png
Drops on death


  • Because his "Bite" weapon engagement radius is set to that of a ranged weapon and Rex has a high PER stat, he will often charge towards enemies from long distances, even if set to a Passive behavior through the Companion Wheel.
  • If Rex dies, the King will have a few solemn words about his passing.
  • Like all cyberdogs, Rex is not affected by pulse weapons.
  • It appears that Rex will not attack giant rats or mole rats if the Courier has the Animal Friend perk. Likewise, despite his apparent hatred for rats, he won't attack Snuffles at Sloan or the occasional non-hostile giant rat running around Freeside.
  • Rex has a unique special attack where he actually tackles enemies to the ground.
  • Rex will growl uncontrollably as if enemies are nearby if you take him into the Silver Rush.
  • Despite Rex's hatred for hats he only reacts with scarce growls towards the Courier if they have any form of headwear equipped.
  • Even though Rex is a cyberdog, non-player characters still talk to him as if Rex was a common human being.


Rex appears only in Fallout: New Vegas.

Behind the scenes

Spare Us the Cutter
  • As the King says, Rex was supposed to hate rats, and go mad attacking them if one was on the current map. The code for this is all in the game, but is deliberately dummied out in VDialogueRexScript. It seems to be quite early code, and doesn't actually work properly if enabled. An earlier attempt at this effect can be seen in the ai package FollowersRexHuntRatsPackage but this doesn't really work either (it just makes Rex randomly search around for a rat rather than running straight to one and attacking). There's also a specific dialogue (!) topic for this - VRexSmellsARat. It seems the ways that were devised to handle this functionality just didn't work so it was abandoned.
  • I believe this effect was meant to be in the game, but was abandoned due to it not working. The reason why is a simple game engine limitation - it's actually not possible to arbitrarily make two characters start combat with each other at long distance due to a lack of a detection event. Basically if two characters can't see each other they can't start fighting.


  • PCIcon pc.png In the course of the quest Nothin' But a Hound Dog, 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. DO NOT DO THIS. Having 2 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.
  • After returning from The Big MT, when trying to talk to Rex, he will bark and will not be able to enter dialogue. To fix this, Crouch and try to talk to/pickpocket Rex and you should enter dialogue.
  • PlayStation 3Icon ps3.png PCIcon pc.png Xbox 360Icon xbox360.png When Rex is acquired, and if you tell him to wait in the Lucky 38 presidential suite, sometimes he will not be there. If this happens, go to the King's School of Impersonation in Freeside where he can possibly be found in the hallways there at which point he runs back to the Lucky 38 instead of fast traveling there.
    • Xbox 360Icon xbox360.png Sometimes simply entering and exiting the King's School of Impersonation will cause Rex to appear and run to the Lucky 38 when you exit.
  • Sometimes, Rex will disappear from the game if you send him to the Lucky 38. Remarks about him will still come from non-player character's and his perk will still be with you, however; you won't be able to fire him meaning you will only have one human follower and will not be able to have ED-E tag along with you (This is because ED-E is a robot and you can only have one human and one non-human following you at the same time). UPDATE: Can now be fixed via the Companion dismissal terminal. Also, in the PC version, you can go to Rex by using the console command player.moveto 0010d8df.
  • PlayStation 3Icon ps3.png Rex may die randomly while in the Remnants bunker
  • PCIcon pc.png Rex loses health when near the Remnants bunker. Fast travel to some other place if you see his health drop.
  • PCIcon pc.png PlayStation 3Icon ps3.png Xbox 360Icon xbox360.png If you dismiss Rex during Nothin' but a Hound Dog, when he is theoretically on loan to you and not a permanent companion, he may disappear and not return to The King. He may eventually show up after traveling to Doc Henry and speaking to him about Rex. Don't travel from The King to Henry and back, Rex still won't be there. When you realize he's gone, load the last saved game, go to Jacobstown and then visit The King.
  • Xbox 360Icon xbox360.png PlayStation 3Icon ps3.png During combat, Rex might chaotically run around from-and-to foes while not attacking anyone. He may also in fact not attack at all when you have him.
  • PCIcon pc.png PlayStation 3Icon ps3.png Xbox 360Icon xbox360.png Rex will sometimes stop moving as if he has been told to wait. You will need to keep checking to see if he is still with you. This can usually be fixed by telling him to wait, then tell him follow you again, fast traveling or going through a door that requires a transition. However these fixes are per incident and he will randomly do it again.
  • Xbox 360Icon xbox360.png While doing the quest You Can Depend on Me (or just trying to sneak into the Gun Runners), Rex may glitch while in combat with the guards and end up in the Vendortron's kiosk. There is no physical way into the kiosk and Rex can still be spoken to. The only way to fix this problem is to fast travel to another location, in which Rex will appear beside you in patched versions of the game.
  • PCIcon pc.png While vilified by the Legion, if Rex simply kills Lupa while you are disguised and have her brain transplanted by Calamity, the epilogue may state that Rex never got a replacement brain even though the quest is completed, rather than the correct ending.
  • Xbox 360Icon xbox360.png When you are knocked out in Dead Money when you escape, you might not be able to find Rex anywhere. He might be found in the lobby of The King's School of Impersonation.
  • Xbox 360Icon xbox360.png If Rex and another person (i.e. the player or another companion) attack the same enemy at the same time and the game goes into slow motion kill-cam, the game may freeze. Turning kill-cam off may solve this problem.
  • PlayStation 3Icon ps3.png Xbox 360Icon xbox360.png Rex may occasionally start unprovoked attacks, even with Passive mode on. Telling Rex to wait a distance from the person can fix this.
  • Xbox 360Icon xbox360.png PlayStation 3Icon ps3.png If you tell Rex to wait outside when visiting Caesar in the quest Render Unto Caesar and you confirm that you want to battle Benny, the game will automatically send you to the ring, and when you win, Rex will be nowhere to be found. He isn't with The King or at any casinos. If you were already at the point in Nothin' But a Hound Dog where you are looking for a new brain, you can still gain a brain as the AI will think you still have Rex, but when you go back to Doctor Henry, he will say he can't perform the surgery without Rex. To fix this in the PC version open the console and type player.moveto 10d8df - Rex is located next to the arena along the outer fence.
  • PlayStation 3Icon ps3.png When acquiring Rex from The King in his room, very top floor of The King's School of Impersonation, he will sometimes drop through the floor and wind up at the bottom level. Just wait a few minutes and you will find him running towards you.
  • Xbox 360Icon xbox360.png PlayStation 3Icon ps3.png If you enter and exit Gomorrah while Rex is following with you and has weapons in his inventory, the weapons may disappear completely even after leaving the casino.
  • PlayStation 3Icon ps3.png Xbox 360Icon xbox360.png For some reason Rex may just randomly die, even outside of hardcore mode.
  • PlayStation 3Icon ps3.png While in combat with an enemy, shooting Rex may cause the game to freeze.
  • PCIcon pc.png Initiating conversation with rex, while in the water, may cause a the game to freeze/crash.
  • Xbox 360Icon xbox360.png While Rex is a companion, the game sometimes freezes when he attacks an enemy.


See also


  1. The Courier: "Something's wrong with my cyber-dog. I was told to come to you."
    Henry: "It's neural degradation. Bio med gel can only preserve a living brain for so long, so you'll need to find a replacement. I haven't left Jacobstown in years, but there was one woman in Novac... Gibson? I remember her living with a pack of hounds. Aside from her, I know that the Fiends and Caesar's Legion fight alongside dogs. There could be viable specimens among them, if you can get to them."
    (Henry's dialogue)
  2. Meet the Companions
  3. Antony: "The mechanical dog you have with you - where did you get it?"
    The Courier: "Rex? I picked him up in New Vegas."
    Antony: "Oh? Such things are common in Denver, but I didn't know that other cities had them as well."
    (Antony's dialogue)
  4. The Courier: "Why do you want to know?"
    Antony: "I ask because Caesar once had a similar pet, but it was lost during a battle."
    (Antony's dialogue)
  5. The Courier: "Absolutely. I'll see that he gets better."
    The King: "I can't thank you enough. Now, there's a few things you should know about ol' Rex here if you're going to be traveling together. First, he hates rats. Can't stand the things. Giant rats, molerats, doesn't matter. He catches a whiff of one and he's off like a shot after them. He's normally pretty obedient, but you might have to chase him some if he goes after one of the little varmints. Second, he doesn't like hats, or the people wearing them. Don't ask. I have no idea why. Maybe because it rhymes with rats. That should be it, though. Other than the occasional bad spot when his brain starts hurting him, that is, but I'm hoping you'll see to that. I wish you both luck. Take care of my Rex now, y'hear?"
    (The King's dialogue)
  6. The Courier: "The King said you could tell me more about his robotic dog."
    Julie Farkas: "Rex? It breaks my heart every time I see him. He's such a good dog."
    The Courier: "So you can't heal him?"
    Julie Farkas: "No, Rex's condition is way beyond anything we can handle. He requires brain surgery, and some sophisticated cybernetics work, too."
    The Courier: "The King brought him here for treatment then?"
    Julie Farkas: "Yes, a few months ago. We had to tell him there was nothing we could do."
    The Courier: "So there's no chance he'll ever get better?"
    Julie Farkas: "I didn't say that. While no one here has that kind of expertise, I do know of one man who might fit the bill."
    The Courier: "Is there anyone who could do all that?"
    Julie Farkas: "There's an old scientist named Dr. Henry who reportedly specializes in this sort of procedure. He'd probably be your best bet. Last I heard, he was living up in Jacobstown, far to the northwest."
    (Julie Farkas' dialogue)