Plot twist: Barney planned the resonance cascade, as he owed so many people beers, he was worried ♥♥♥♥ would hit the fan if he didn't buy them all beers. So, he decided he had to kill them before they got impatient. He planned the resonance cascade. He put a beer right in the center of the machine the day before the resonance cascade, the next day, the beer I owed ya caused the laser to get contaminated, as it all evaporated into the beam when the glass broke. The beer then made contact with the crystal. With the crystal contaminated with such mutated alcohol, the crystal literally teleported an entire race of aliens onto Xen. Xen was never the border-world. G - Man just thought that it was, he didn't go to school, he's a being from another dimension, why the ♥♥♥♥ would he do that? The aliens had teleported from the border world and right into Xen. And then one alien thought, "I have a great idea! I'm gonna grow extremely large and become a giant demonic baby fetus that shoots lasers!"
And then, a bunch of aliens teleported to Black Mesa. Meanwhile, Barney was shooting scientists in the face and then traveling back in time to do it again. Barney was in the elevator at that time, and when he came across houndeyes, he thought he could control them. He failed, and they tried to murder his ass. He beat the living ♥♥♥♥ out of him with that beer I owed ya (He already bought a couple of beers before realizing he needed the rest of his money to buy Mc Donalds)
Then he met Rosenburg, he didn't kill him because he decided that this plan failed and that maybe these guys will forget about his debt to them. Later, after escaping, Rosenburg asked him about the beer. And.. Well.. That's why Rosenburg and the other scientist aren't in Half Life 2. He realized that nobody would ever forget his debt, and he had to kill them, thus the real reason why there are no other scientists in HL2. Barney was making a ♥♥♥♥ ton of noise while dancing to some really loud music in his underwear, and the combine heard it and were all like, "HEY! KEEP IT THE ♥♥♥♥ DOWN!' But Barney didn't listen. So instead of calling the police or something, the Combine decided "♥♥♥♥ it. Let's start a war with the entire damn planet." and that happened.
The reason the Houndeyes and Bullsquids are all gone is because Barney had such loud music, that they all went back to Xen. The Combine tried to murder Barney after they were done with the war, but Barney just decided to borrow one of their suits, and put it on. The Combine instantly said, "Oh, nevermind. He's a CP. Welp, guess we did this for nothing." And the other Combine is like, "Wait. We're just gonna go home after all this? I thought our entire goal was to murder this ♥♥♥♥♥♥♥♥." and the other guy is like, "Well, what else could we do?' so the other Combine goes, "...I have no idea. I don't know." So the other one says, "..Ya know what? ♥♥♥♥ it. Let's enslave the entire planet or some stupid ♥♥♥♥ like that, and let's turn everyone into weird looking naked things that shoot lasers." So the other Combine says "That's not what I had in mind at a-"
"Shh.. SHH. Just don't question it."
Eventually, Barney realizes that they had a fetish for naked guys with Metal limbs that shoot lasers, and decides "♥♥♥♥ these guys, they ♥♥♥♥♥♥ suck." And then he says, "Catch me later and I'll buy ya a beer" and jumps out of the Citadel. Later he finds Kleiner, another guy he owed a beer to. He was going to kill him, but then Lamarr came in, and Barney was all like, "IT'S YOUR PET THE FREAKIN HEAD HUMPER!" and so that's why Barney doesn't kill Dr. Kleiner, because if he does, then Lamarr would have to find someone else to bug, which would probably be Barney. He tries to kill Eli, but every time he he gets splashed with water while going by an army of CPs with guns, a Chopper that shoots ♥♥♥♥, and a tank that likes to shoot missiles at people, and he has to go back and change clothes. Eventually, he gave up. He would've tried the teleporter, but he still has nightmares about that cat. Then he finds Gordon, and tries to murder him. He succeeds, but then he realizes there's a dead body on the floor, so he throws it in front of a train to make it look like he got killed by the train, but.. Gordon fell through the glass and went right into the train, because as he fell behind the train, his shirt got stuck on the glass, and eventually the glass broke, because one of his buttons came loose and fell right onto the glass, breaking it. Why is his button so heavy? Well, how else is he supposed to work out enough to literally smash an animal into nothing but organs with like, 4 swings of a crowbar? He ends up falling into the train, and then G man realizes "♥♥♥♥, he fell asleep? God ♥♥♥♥♥♥♥ dammit." so he wakes him up. "Rise and shine, Mr Freeman." and he comes back.(That's why the dude didn't see Gordon get on) Barney sees him again, and decides to do the exact same thing, but as he's backing behind to the control panel, he accidentally presses the buttons to call Dr. Kleiner, and soon Dr. Kleiner would pick up and see Barney murdering Gordon. So Barney decides to play it cool, and tells Gordon "About that beer I owe ya", in order to clear up that there are no hard feelings about the beer thing. So then later, Barney gives him a crowbar (He was trying to smash Gordon's head in by dropping it on him, but he failed), so then after Gordon does ♥♥♥♥ and things, during Episode 2, Barney finds out that Dr. Magnusson is still alive. So he tries to murder him. Little did he know that Dr. Magnusson has a microwave casserole, and he shoved it up Barney's asserhole. The casserole was so hot, it burned Barney to death. And that's why Barney isn't in Episode 2. Dr. Magnusson realizes that Gordon's plan all along was to have Barney get a casserole shoved up his ass, before the events of Half Life 1, he was always trying to get Barney to get a casserole shoved up his ass, because he ♥♥♥♥♥♥♥ hated Barney. He microwaved Magnusson's casserole so that it would explode, causing him to have to get a new one. However, Gordon had locked the microwave somehow to always heat things up super high, causing the casserole to stay hot for 20240828583578937593798 years. He also told Magnusson about how Barney was a ♥♥♥♥♥♥♥♥♥, and how shoving a casserole up his ass would shut him the ♥♥♥♥ up. He also found a picture of Dr. Magnusson online, asked Dr Kleiner for the exact path of winds for the day, and threw the picture completely perfectly and specifically. Later, Gordon had killed zombies in Ravenholm, and arranged their arms so that when the photo got there, it would bounce on their claws and fly right up onto a roof, where a headcrab would be fooled and would think it was really a human and not a photo, cause headcrabs are ♥♥♥♥♥♥ stupid, even though these crab creatures have unique parasitic strategy. The headcrab jumped towards it, knocking it even further into the air. Gordon had also heard that Barney had to "look after Dr. Kleiner". So he made sure that the photo would reach Barney at the exact time he walked by. He knew that as the Combine approached, they would shoot at the base, and would also shoot the photo right towards Barney, after Barney had killed all Combine, he found the photo of Magnusson. And after you meet up with him again, he isn't fighting the war, he's just trying to get to Magnusson, and he needs to shut down the damn shields to do it. Magnusson gets pissed at this, and that's the real thing he was talking about when he said, "Involving a certain microwave casserole". But then, Barney's ghost got pissed, so he found an advisor, and told him, "Hey, catch me later and I'll buy ya a beer." Later, the Advisor gets mad because he never got a beer, he tells his best friend about it, and they decide to find it. Then they see a huge ♥♥♥♥♥♥♥ rocket ship thingy thing or whatever, not sure what it was but ♥♥♥♥♥♥♥♥♥ it just closed the ♥♥♥♥♥♥♥ portal, so they follow the smoke that the r