Codex Gamicus
Isaac Kleiner

HalfLife2 IsaacKleiner.jpg
Doctor Isaac Kleiner, as depicted in
Half-Life 2.

Game series Half-Life series
First appearance Half-Life: Decay
Occupation: Scientist
Species: Human
Gender: Male
Voice actor(s): Harry S. Robins

Doctor Isaac Kleiner is a fictional character from the video games Half-Life and Half-Life 2. An archetypal 'absent-minded genius scientist', he is a prolific author of several works on teleportation travel, and one of the few survivors of the incident that took place in the Black Mesa Research Facility. Later on, he becomes a key leader of the Resistance against the Combine Empire, and a prime member of the Resistance's science team.

He is affectionately referred to simply as "Izzy" by Dr. Eli Vance on various occasions. Some sources also erroneously refer to the character as Dr. Alex Kleiner, based on an apparent inaccuracy in the strategy guide of the original Half-Life.

Appearance and role[]


Although Dr. Kleiner's character design is based on the "bald, glasses" scientist model from the original Half-Life (dubbed "Walter Bennett" by fans of the Walter's World series of fan fiction and later named as such in the Opposing Force and Blue Shift expansion packs) he is not intended to be the same character, and never interacted with Gordon at all during the Black Mesa Incident. Also, the texture file for Dr. Kleiner's face is called "walter_face.vtf". This is likely to be referring to Walter Bennett. Before Half-Life 2, the only reference in the games to Kleiner was during Half-Life: Decay when Dr. Keller mentions he "[does] not understand what Kleiner sees in that boy," referring to Gordon.

Dr. Kleiner, who was one of Gordon Freeman's professors at MIT, recommended him for employment at Black Mesa by the Civilian Recruitment Division (as the computer voice on the tram mentions) and worked with him as part of the facility's Anomalous Materials team. He manages to survive the Resonance Cascade disaster of the first game with the aid of Eli Vance, though exactly how he escapes is unknown.

Half-Life 2[]

Along with colleagues (and fellow survivors) Alyx Vance, Dr. Eli Vance, and Barney Calhoun, he makes up the core of the resistance against the Combine. Dr. Kleiner has set up a lab underground in City 17 in an old abandoned Northern Petrol building. A teleportation system, developed jointly by Kleiner and Vance, allows for near-instantaneous transportation between Kleiner's lab and Vance's facility, several miles distant. As a pet, Dr. Kleiner keeps a debeaked headcrab he calls 'Lamarr' and at some points in the game calls 'Hedy' (a reference to 1930s actress and inventor Hedy Lamarr).

A depiction of Kleiner's younger self is also featured in Half-Life 2, appearing on the cover of Popular Scientist, a fictional magazine (and spoof of Popular Science and New Scientist magazine) that would have to be published prior to the Black Mesa Incident. In it, he sported sideburns and had more hair, which is seen as brown in color. [1] Though he has no active fighting role in the game, he is seen holding a shotgun when Gordon and Alyx arrive at his lab, just after escaping Nova Prospekt.

Half-Life 2: Episode One[]

Doctor Isaac Kleiner giving a Kleinercast in Episode One.

In Half-Life 2: Episode One Kleiner returns, appearing on the video screens previously reserved for Dr. Breen's propaganda and instructing survivors to make their way to their nearest train station to evacuate City 17. Kleiner also amusingly informs people that the Combine's "Reproduction Suppressors" are no longer effective, and that "[For] those so inclined, now would be an excellent time for procreation" and to "do your part for the revival of the species". He also rallies people to prepare for the Combine's retaliation, stating that several new technologies were developed during their occupation, and that these will be deployed as soon as possible to help fight the Combine.

Half-Life 2: Episode Two[]

Kleiner also appears in Episode Two, where he is working out of the White Forest Rocket Facility with Eli Vance and Arne Magnusson on a device intended to close the Combine superportal created as a result of the events in Episode One. He mostly appears during radio transmissions while guiding Alyx and Gordon to White Forest, and from that point on as a regular NPC. He also argues bitterly with Magnusson frequently, whom Vance states was Kleiner's rival at Black Mesa. Upon the discovery of the Borealis in Judith Mossman's decoded message, Kleiner expresses a wish to use whatever power resides in the ship against the Combine, opposing Eli's express desire to destroy it in order to prevent "another Black Mesa."


An early model of Dr. Kleiner, with slightly different facial characteristics.

His human voice in Half-Life 2 was provided by Harry S. Robins, the voice of all scientists in the original Half-Life.

At the end of the Half-Life 2 chapter entitled "Entanglement", Dr. Kleiner is shown poking his head through a door in his lab while holding a shotgun in a possible nod towards the original Half-Life. A scientist at the end of the "Lambda Core" chapter of the original game is shown holding a shotgun in a similar, scared fashion, and is spawned as the scientist model that Dr. Kleiner is based on .

Half-Life 2: Raising the Bar reveals that his model was based on Ted Cohrt, "an accountant who worked in the firm above Valve's office" with two sons who were Half-Life fans.

Many of Kleiner's catchphrases appear to be the same or modeled of Dr. Brown from Back to The Future as well as several of his mannerisms. Its is unknown if this was intentional on Valve's part.

Kleiner is also extremely similar to the character of Dr. Bunsen Honeydew, of "The Muppets" fame, with the same vocal mannerisms, cavalier attitude towards assistants, and fascination with teleportation.

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