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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 was eventually enhanced.



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]


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 goes berserk immediately after and jumps on a Combine Dropship whilst trying to attack it, departing into the unknown. It is worth noting that this whole scene – unlike other sequences where supporting characters fight alongside Gordon – is entirely scripted, and as such requires no involvement from the player at all.

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 casing of the Strider's control mechanism and subsequently shuts it down 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 manage to also kill Gordon and Alyx, Dog shows up in the nick of time, narrowly avoiding the death of Alyx. 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.

Personality and skills

Dog, much like a real 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. 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. When either he or Alyx is threatened, he can be a dangerous foe, using his immense strength and weight to smash enemies to the ground or tear them apart. This makes him a crucial asset in any battle, as he can destroy Striders with ease and hurl heavy objects at targets.

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.

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.

Ep1 citadel 000018

Alyx and Dog at the foot of the Citadel.

Alyx treats Dog much like a pet dog, 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. Their relationship is also much like that of a dog and its master; they have a mutual trust and friendship, which has grown over the years so that Alyx now trusts Dog's opinions and hunches, as crazy as they may sometimes appear. She also has come to accept his sometimes erratic behavior, when he runs off without warning only to appear again moments later. Their relationship differs from the traditional dog and master relationship in the sense that Dog is considerably more intelligent than most real dogs, and is also much larger and more powerful than any human. However, these differences rarely come between them and their friendship seems very deep, so much so that Alyx shows many signs of affection for Dog. He also seems to have something of a sixth sense, being able to determine where Alyx is, no matter the situation. When Alyx is inside the Citadel, he is eager to get in and rescue her.

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. He has immense strength, and proves extremely useful through the course of the story, as he can throw large objects (such as vehicles) at enemies or make way to areas which are otherwise inaccessible to Gordon. His thick plating and large size render him invulnerable to most threats he may encounter.

Behind the scenes

Dog concept

Concept art.

  • Dog does not have any combat AI - all in-game fight scenes with Dog are scripted. If a spawned Dog is approached by anything threatening, even a common Headcrab, he will flee. If no enemies are present, he will find a nearby 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]

Related achievements

Half-Life 2

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

Half-Life 2: Episode Two

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


  • Although Dog is seemingly invulnerable to damage, he simply has a huge amount of health to make sure he does not die (as opposed to using very fast regeneration of health, as Alyx does). 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 will appear.
  • The aggressive roars that Dog makes when provoked are very similar to the noises that Striders make.
  • If the player hits or attempts to grab Dog with the supercharged Gravity Gun, corpses of Dog will appear, as he is a machine that's not supposed to be grabbed.




Half-Life 2

Half-Life 2: Episode One

Half-Life 2: Episode Two

List of appearances


Half-Life Wiki has more images related to Dog.
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