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"First model was about yay-high. I've been adding to him ever since."
Alyx Vance[src]

Dog is Alyx Vance's "pet" robot, built by her father Eli to protect her when she was young and progressively enhanced since then.



Dog is a robot, built by Eli Vance to protect his daughter Alyx when she was a child. Dog's original model was around one meter in height, but as Alyx grew older, she began adding upgrades and new parts to Dog, and he towers around 2.5 meters tall at the time of Half-Life 2.[1] Dog has a Zero Point Energy device, much like the Gravity Gun, built into one hand so that he can pick up and throw things. Dog's body is constructed largely of scavenged scrap metal, hydraulics and wires. He has what appears to be a scrapped Combine City Scanner for a head, though with only three flaps while normally Scanners have four. He is quadrupedal, walking on his knuckles like a gorilla, but can balance himself on his hind legs if it is needed, such as when he's lifting a heavy object.


Half-Life 2[]

Dog Alyx BME

Alyx and Dog in the Black Mesa East scrapyard.

Gordon Freeman is first introduced to Dog in the Black Mesa East scrap yard. As part of a tutorial on operation of the Gravity Gun, Alyx arranges a game of "fetch" between Gordon and Dog, using an inert Combine Rollermine as the ball, until they are interrupted by a Combine assault on the Resistance facility. After heading back inside, Dog opens the door into an unused tunnel leading towards Ravenholm for Gordon to aid his escape, after he gets separated from Alyx. While Gordon enters the tunnel, Dog stays behind to help Alyx and the others defend the lab.

Gordon meets Dog again after he and Alyx teleport from Nova Prospekt to Kleiner's Lab at the end of the chapter Entanglement. The company splits once more when Gordon and Dog set off to find Barney Calhoun, Alyx deciding to stay with Dr. Kleiner who refuses to leave without his pet Headcrab Lamarr. As the chapter Anticitizen One begins, Dog is quick to leave Gordon behind and charge at a nearby group of Combine troops outside the lab, tossing a ruined car at them and even fighting off an APC. He then forces open a Combine Barricade gate for Gordon, allowing him to proceed. However, Dog is sidetracked by a landing Dropship carrying Overwatch soldiers and closes the door on Gordon to attack the landing soldiers. Dog then attacks the departing Dropship, now without cargo, and ends up being carried away by the synth to the unknown.

Dog eventually manages to find Barney, and Gordon meets both of them in the square toward the end of the chapter "Follow Freeman!", in a scene where Dog, in the heat of the battle, knocks over a column topped with the large statue of a horse. As Barney reports to the player, Dog is probably aware of the fact that Alyx is already in the Citadel, and so tries to reunite with her, being completely uncontrollable by others. The last time Dog is seen in Half-Life 2 is when he once again opens a passage for Gordon, this time allowing him to proceed to the Citadel's foot, by lifting a heavy section of Combine Smart Barrier, uncovering an ancient sewer tunnel.

Half-Life 2: Episode One[]

Hl2ep1 alyx+dog

Alyx conversing with Dog.

Episode One opens with Gordon lying in the darkness under a pile of rubble. The sound of Alyx and Dog searching for him leaks through, and after lifting up a large slab of rock, Dog's head and eye appear through a hole. He seems elated, and quickly lifts Gordon out of the rubble.

After Gordon's recovery, Dog helps Alyx contact her father, using his metal body as an antenna by twisting his hand to get a better signal. After much deliberation, Alyx and Gordon decide to enter the Citadel, however they are blocked by a large ravine. Dog runs off in search of something, and soon throws over a large empty car. Testing the distance by throwing a rock over the ravine, he lets Alyx know that her and Gordon are to climb into the car, allowing him to throw them over. Eventually Alyx concedes, telling Dog to go back to Eli after he has thrown them. Gordon and Alyx both get into the car, before Dog picks it up and throws it across the dividing ravine. Dog is not seen again for the rest of the game.

Half-Life 2: Episode Two[]

Dog vs Strider Outlands

Dog about to prove his strength against a Strider, as seen in the Episode Two trailer.

In Episode Two, Dog appears late in the game in the Outlands, when Gordon and Alyx have nearly reached White Forest. When the duo is forced to stop their car because of a gate, a Strider that was lying on the ground wakes up. Fortunately, Dog appears quickly and takes down the Strider in an epic battle, with little regard for his own well-being. After narrowly avoiding being crushed multiple times, he manages to tear off the Strider's carapace and subsequently kills it by removing its brain.

Afterward, Dog challenges Gordon to beat him to the base in his car. If the player is able to beat Dog, Alyx will mock Dog by saying "Better luck next time, slow poke." However, if Dog wins, he will dance around triumphantly. Dog is then left outside to help MIRT patrol the area while Gordon and Alyx continue on to meet Eli and Kleiner.

Towards the end of the game, after the closure of the Superportal, Dog appears once again. He greets Alyx but is distracted by something in the distance, and goes running off much to Alyx's dismay. Whilst Dog is gone, Eli, Gordon and Alyx go into the hangar to get to the helicopter, but are ambushed by Combine Advisors who kill Eli, inserting their appendage through the back of his neck, breaking his spinal column. Before the Advisors could kill Gordon and Alyx, Dog re-appears and saves them. He manages to injure one Advisor considerably, jumping onto its back and smashing it to the ground, whilst the other flees from his attacks relatively unscathed. As Alyx cradles her dead father, Dog leans over, watching in confusion and sorrow.

Half-Life: Alyx[]


Sketch of Dog in Half-Life: Alyx.

Inside Alyx's observation room are some designs of Dog during his various stages of construction. Alyx also has a photo of Dog in his earliest constructed form.

In the post-credits sequence, Dog physically appears. He swings into the hangar, jumping off the helicopter and gives the crowbar to Eli, who hands it to Gordon before declaring they have a lot of work to do.

Personality and skills[]

Much like a real dog, Dog is very friendly, loyal, and has an intelligent and excitable personality. Similarly to Barney Calhoun, Dog provides comic relief throughout the games with his quirks and many strange and odd decisions, even dancing when he is looked at for a period of time. One of his main forms of emotive outlet is his eye, which has an aperture used in much the same way as the human eye to show feelings by opening and closing. His head flaps also move according to his mood. Dog makes friendly and playful noises such as beeps and whines, emulating the sounds made by a real dog, especially when he is around Alyx. Dog shares a very close relationship with Alyx, often asking her to play along with him. Alyx treats Dog much like a pet, calling him "boy" and using similar body language and voice as when talking to a real dog. She pats her upper thighs when calling him at Black Mesa East, and tells him to "fetch" when Gordon throws the Rollermine.

Where Dog differs from the average pet is his intelligence. Dog is a highly inquisitive and resourceful creature and is able to figure out solutions to problems, as unothodox as they may be, such as throwing Gordon and Alyx across to the citadel on a rundown car. Alyx also implies that Dog is able to perform calculations, where in the same situation she suggests that Dog has "done the math", though Dog quickly refutes this. Nevertheless, Dog and Alyx have a mutual trust and friendship which has grown over their years together which makes Alyx now trusts Dog's opinions and hunches, as crazy as they may sometimes appear.

Ep1 citadel 000018

Alyx and Dog at the foot of the Citadel.

Like a real dog, Dog is also very protective of his master and by extension those she holds dear, like Gordon Freeman or Eli Vance. When angered he can be a dangerous foe to those who anger him, using his immense strength and weight to smash enemies to the ground or tear them apart. Despite his seemingly haphazard construction, Dog is a highly durable combatant with strong offense and defense. Dog can withstand gunfire and powerful impact without a visible scratch, and is able to use his strength to devastating effect against similarly durable targets like Combine synths. Dog is also highly flexible and agile which helps when dealing with enemies larger than himself. All of this in combination with his intelligence make Dog a very powerful asset for the Resistance that can take down powerful enemies which would normally take a huge amount of effort for humans to take down.

Behind the scenes[]

Dog concept

Concept art.

  • Dog does not have any combat AI and all in-game fight scenes with him are scripted. If spawned through console he will just run away from any threat. If none are around he would find a small object and throw it at the player, as if playing fetch.
  • As mentioned in the Half-Life 2: Episode One commentary, players' feedback towards Dog were very positive. As a result, Valve made him the first thing to be seen at the start of the next game.[2]
  • Dog was one of the few Half-Life 2 concepts that went through very little revision before being finalized for the game. Designers were inspired by classic movie robots, such as Robby from Forbidden Planet.[3]
  • Early texture sheets from the playable Half-Life 2 Beta show that Dog was to feature other colors, such as aqua blue, maroon, pink or green. His head was also to be made out of a scrapped Combot, the direct predecessor to the City Scanner.[4]
  • One of Dog's concept designs in Alyx's apartment in Half-Life: Alyx is a reference to the robot dog in Valve's VR game The Lab.

Related achievements[]

Half-Life 2[]

Hl2 makeabasket
Two Points 2 Gscore
Use Dog's ball to make a basket in the scrapyard.

Half-Life 2: Episode Two[]

Ep2 beat racewithdog
Pedal to the Metal 5 Gscore
Beat Dog in a race to White Forest.


  • Dog is not invincible. He simply has a huge amount of health. It is possible for him to die, but this can only be observed if the player spawns him using the console in a combat situation that he would not normally be involved in.
    • If Dog takes damage, smoke effects will appear (Possibly reused from the cut Combine Guard).
  • The aggressive roars that Dog makes when provoked are very similar to the the Strider's audio.
  • If the player hits or attempts to grab Dog with the supercharged Gravity Gun, corpses of Dog will appear as he is not supposed to be affected by it.




Half-Life 2[]

Half-Life 2: Episode One[]

Half-Life 2: Episode Two[]

Half-Life: Alyx[]


List of appearances[]


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