He eventually becomes one of the leading figures in the resistance, almost single-handedly destroying the Combine prison, Nova Prospekt and signaling the uprising to begin.
Gordon Freeman's final character model is based on Valve employee Chuck Jones including his, at the time, pony tail in Half-Life 1.
He plays the role of an overseer and employer, both observing the player as the games progress and pulling strings to control the outcome of specific events throughout the Half-Life saga.
The G-Man's constant appearances in the Half-Life games, as well as his revealing monologues with series protagonist Gordon Freeman, imply that he is of great importance and somewhat anchors the efforts of the player.
Scott Lynch, Valve's chief operating officer, lent his face to the game for use in-game as Barney in Half-Life 2.
Barney's name stemmed from the earlier alpha versions of Half-Life in which the model for the security guards held a resemblance to actor Don Knotts, inspiring comparisons with Knotts's character Barney Fife from The Andy Griffith Show, which in the United States has long been a disparaging term for an inept policeman or security guard.
In Half-Life: Blue Shift, the playable Barney progresses through Black Mesa to escape the events of the Resonance Cascade and is able to do so, in contrast to Gordon Freeman and Adrian Shephard, who are held in stasis.
However, the Bell Boeing V-22 Osprey transporting him is hit by a Xenian energy blast and crashes; he is rescued by a group of Black Mesa scientists, and due to never making it to his designated landing zone, Shephard remains unaware of the secret orders to kill all BMRF employees.
Immediately after the disaster, Rosenberg converses with Dr. Keller and makes it clear that he believes their greatest responsibility should be the safety of the people at Black Mesa.
Although Keller thinks that they should attempt to reset the displacement fields first, he eventually agrees with Rosenberg, and they come up with a plan to contact the military, so that they can help and evacuate the facility as soon as possible.
They first escort Rosenberg to the surface to contact the military, and then under the guidance of Dr. Richard Keller, they succeed in starting a resonance reversal to help lessen the effects of the dimensional rift.
In Half-Life: Opposing Force, Adrian Shephard finds Cross's corpse in Xen after being teleported there by the Displacer Cannon, which implies that she died sometime after the events of Decay.
Dr. Gina Cross also enters the same room to fix a jam in the specimen delivery system's lift mechanism, meaning they are both in the same place when the Resonance Cascade finally occurs.
As Adrian Shephard traverses within Sector E of Black Mesa, he enters a testing laboratory where Xen specimens were being experimented on prior to the Resonance Cascade.
He opens up a transmission intended for Dr. Bennett, revealing a hologram of a scientist talking about the results of an experiment conducted on a Barnacle, which was one of the Xen creatures being examined.
Dr. Kleiner was one of Gordon Freeman's professors at MIT, recommending him for employment at Black Mesa to the Civilian Recruitment Division and working with him as part of the facility's Anomalous Materials team.
In Episode One, Kleiner appears on the video screens previously reserved for Dr. Breen's propaganda and instructs survivors to evacuate City 17, also encouraging them to procreate.
In Episode Two, Kleiner 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 by the Citadel's destruction.
He mostly appears during radio transmissions while guiding Alyx and Gordon to White Forest, and argues bitterly with Magnusson, whom Vance states was Kleiner's rival for grant money at Black Mesa.
Upon the discovery of the Borealis in Judith Mossman's decoded message, Kleiner expresses a wish to use the technology residing in the ship against the Combine, opposing Eli's vehement desire to destroy it in order to prevent "another Black Mesa".
He wears a prosthetic that replaces his left leg beneath the knee, which was lost when he was attacked by a Bullsquid while helping Dr. Isaac Kleiner climb over a wall into a Combine city.
Dr. Judith Mossman (voiced by Michelle Forbes) is introduced in Half-Life 2 as a physicist working with Eli Vance at the Black Mesa East Research Facility.
Colonel Odessa Cubbage (voiced by John Patrick Lowrie) is a member of the Resistance against the Combine who speaks in distinct Received Pronunciation.
When Gordon Freeman arrives at New Little Odessa en route to Nova Prospekt, Cubbage is briefing members on the use of the rocket launcher against Combine gunships.
[10] He speaks enthusiastically about "tending to his flock", i.e. dispatching the remaining zombie inhabitants of the city with a Winchester Model 1886 and homemade traps while offering them consolatory words.
He helps Gordon Freeman intermittently in Ravenholm, giving him a shotgun, combat tips, and advice mingled with biblical quotations.
After waving Gordon off, Grigori continues fighting the hordes of enemies until he retreats into a nearby tomb, ignites a wall of fire around it and disappears, laughing maniacally.
The Half-Life 2 art book, Raising the Bar, has information that indicates Breen used, at least at one point of the planned story if not in the final version, a radio transmitter tower on the surface (i.e., not in Black Mesa) to communicate directly to the Combine and negotiate a surrender.
One of the slides would have shown Breen at the foot of a tower wearing a headset linked directly to it, with arms held wide and speaking to the skies.
It was also mentioned in one of the "Breencasts" to the Sector Seventeen Overwatch in Nova Prospekt; "I have good reason to believe that in the intervening years, he was in a state that precluded further development of covert skills."