* One of the rebels who you first encounter, and who is severely injured, is named Winston. Winston Smith is the protagonist in the novel ''Literature/NineteenEightyFour'', which inspired City 17's harsh brutality of civilians, and heavy surveillance.
* One of the quotes you can hear the citizens saying is "Sometimes, I dream about cheese." This seems random at first but considering [[CrapsackWorld the setting of Half Life 2]], it is unlikely citizens are able to get cheese, or any kind of remotely tasty food for that matter hence cheese haunting their dreams.
* Isaac Kleiner's name for his pet headcrab, Lamarr, seems random at first, until he mentions towards the end of the game that another name for her is "Hedy", meaning she's named after Hedy Lamarr, an actress from the 1930s to the 1950s. At first, it seems like a lame pun (''Head''-y Lamarr), but Hedy Llamar was also an inventor who's responsible for broad-spectrum technology that's the precursor to Wi-Fi. Kleiner, being a scientist, probably held her in very high regard for this achievement, and named Lamarr in tribute to her scientific achievements (and partially for the pun).
* Besides the drain on the world's resources by the Combine, something which was even toned down from miles upon miles of dead earth in the beta/leak, there's also ''insane'' amounts of irradiated water and waste filling up entire canals and areas as Gordon rides around on the airboat. The HEV Suit protects him, sure, but what about all the rebels and their stations that are built around these radiated materials? They wear nothing but civvies or stolen vests and clothing, and the very person who prepares the airboat for you is just in an open end of the canal, on some wood boards inches above entire waist-deep pools of the stuff.
* Most of the characters you meet during the game seem to be around the same age, give or take a few years, probably between 20 and 30 (we'll say 25 for argument's sake). Given that almost 20 years have passed since the first game, that would put most of the people the player encounters at the age of 5 when the events of 'Half Life 1' occurred. That game was scary enough for an adult to experience, imagine being a child and waking up one day to find that mummy and daddy have been turned into slobbering zombies with their guts hanging out, your small town is in the process of being obliterated by alien war-ships and the marines are gunning down anything that doesn't look human.
* Those weird screams headcrab zombies make? [[https://www.youtube.com/watch?v=md1afDGmUXA They're in English, reversed.]] Play them backwards, and they're actually ''[[AndIMustScream the anguished screams of the headcrab's host.]]'' That's right, headcrab zombies are not only not dead, ''they're fully aware of what they're doing and helpless to stop themselves.''
* [[Headscratchers/HalfLife2 See here.]]