Half-Life (series)/Funny

"Alyx: Well, Gordon, unless you have a better suggestion...he is a robot, he's done the math. Alyx: You did do the math, right? Dog: *Shakes head no*"
 * In the beginning of Episode One, Dog suggests getting Alyx and Gordon into the Citadel by tossing a car (with them in it) across a gap into the building.
 * Turns to Dog*

""Now would be an excellent time for procreation! That is to say, in layman's terms, you should seriously consider doing your part for the revival of the species." "Did Dr. Kleiner just tell everyone to... get busy?""
 * In addition, if you listen to the developer commentary, you'll find out that this joke started because of a glitch in which Dog's head shook back and forth after Alyx mentioned him doing the math. The play testers loved it so much that Valve made it official.
 * Also in Episode One, Kleiner is making a televised announcement and mentions the benefits of removing the reproduction suppression field the Combine had in place.

""Oh, back so soon?""
 * Referenced in Episode Two's recap of One, which has Dr. Kleiner saying "Now would be an excellent time for procreation!" while the city's on fire and Combine are running around shooting everyone.
 * You can derive great fun from throwing things at the officers in Half-Life 2.
 * Let's see: You've got standard objects like exploding and non-exploding barrels, but there are also things like tires and boxes. And if you're just feeling slly, you can toss paint cans at them!
 * In Episode 2, where you have to help Greggs and Sheckley fight off the Antlions, after, Greggs yells "Alright Gordon, be adequate!", to which Sheckley asks him what the hell that means. Greggs simply replies, "I don't know, sounds like something the Vortigaunts would say."'
 * When you enter the Victory Mine, you see these little immobile grubs all over. Because you can easily kill for health and there's even an achievement for getting all them, you'll probably try and kill as many as possible. When you reach Griggs and Sheckly's outpost they say the Antlions don't make themselves too much of a problem so long as you don't mess with their grubs. Whoops.
 * In Episode 1, there is a moment where you have to crawl up the air ducts and temporarily leave Alyx behind; however, if you go too far down the wrong path you fall through, in the same room where you started from right in front of Alyx.