Robin Williams was a huge fan of the Half-Life series and held talks to do voice work in the games. However, due to his busy schedule, the project never came to fruition.
Half-Life 2 holds the title of the highest-rated PC game of all time. It is still regarded as a masterpiece by critics and players alike.
When you listen to the screams of Headcrab victims in reverse, you hear them shouting 'help me.' This shows that the victims are still aware of their surroundings and the terrible pain they are enduring.
In the game's original opening scene, the player began on a hill near a utopian modern city. As the G-Man spoke, the sky reddened and darkened, the city was cloaked in black, and with a flash of lightning the Citadel appeared in the middle of the city. The player arrived in City 17 by train, after a journey reminiscent of the long train scene in the first game.
When you first meet Barney, he says, 'About that beer I owed ya...' This is a reference to the original Half-Life; one of Barney's pre-disaster idle lines was 'Hey, catch me later, I'll buy you a beer.'
The game had to be activated through Valve's Steam system as an anti-piracy measure. On release day the system crashed under the load, and players were unable to play the game for hours.
In an early script draft, Gordon Freeman was shown by Eli Vance, through slides, what had happened during the lost time period. The slides showed Bullsquids chasing people, an Icthyosaur appearing in a pool, and how Dr. Breen seized power. This section was cut for the sake of the game's pacing.
In the game, Gordon Freeman has no model or texture other than his hands. Although a grey, untextured model can be created in Garry's Mod, the game itself prevents the player from seeing Freeman's face or body.
The reason the game was delayed from September 2003 to November 2004 was not the theft of its source code, but that the game was not yet finished. The leak was simply an unfortunate coincidence.
Some of the gas pumps in the game are in Swedish: instead of 'total sales' they read 'summa', the currency is the 'krona', 'volume' is written as 'volym', and liters are used.
During development, 12 weapons were cut from the game. Among them are the MP5 and the OICW, seen in beta footage.
Dr. Kleiner's pet Headcrab is usually called 'Lamarr.' However, while searching for the escaped animal, he says, 'There's only one Hedy.' This is a reference to Hedy Lamarr, the actress and pioneer of communication; she is considered the first inventor of spread spectrum technology.
Gordon Freeman is a silent hero throughout the entire series. When Alyx Vance first meets him, she makes a humorous nod to this with the line, 'You're a quiet one, aren't you?'
The Combine conquered the planet by defeating Earth's military forces in just seven hours. This conflict was called the 'Seven Hour War.'
Originally, Alyx's father was a military captain who worked at the Combine Air Exchange Facility but secretly helped the resistance. When the Air Exchange Facility chapter was cancelled, Captain Vance was removed entirely and Eli became Alyx's father.
The submachine gun in the game is based on the real Heckler & Koch MP7. The real MP7 can be carried like a pistol, fired with low recoil, and used like a rifle with its stock extended.
In the water hazard sequence, interacting with the 'all-knowing Vortigaunt' you encounter gives you mysterious answers. Lines such as 'The eyes of the far-off look behind yours' and 'A secret guides us both, we will not speak its name' break the fourth wall and address the player.
In the 'We Don't Go to Ravenholm' chapter, the name of the priest Grigori, who helps the player, is an old Christian name and means 'watchful' or 'alert' in Latin.
In one scene, Barney says, 'I still have nightmares about that cat,' and then mutters, 'Did you just hear a cat?' This may be a reference to Schrödinger's cat thought experiment or to the teleported cat in the 1959 film 'The Return of the Fly.'
The development process of Half-Life 2 took a full six years.