Kenny/Kyle as usual, tons of storytelling. Read and enjoy. Sorry for the crappy summary.

Kenny, Kyle, Stan and Cartman had been and would always be best friends. They grew up together, stood together when it really mattered and did everything together. However, as they grew up, their tastes changed.
As children, they used to play together and pull pranks on other kids. Nowadays, they went to strip clubs and bars together. They were happy to be able to do "grown-up stuff" now, but they would never say it out loud, as it would seem "childish".
Unsurprisingly, Kenny was the one who drank the most of the group. He had already tried every street drug and alcoholic drink before he even turned 14; he was just happy to be able to do the latter with his friends now.
Cartman and Stan, on the other hand, knew when to stop... most of the time.
Kyle, as the most careful one of the group, didn't smoke at all and didn't drink nearly as much as the rest of them. He figured that someone had to drive everyone home when they could barely walk in a straight line without help, although only Kenny used to drink that much, since his parents didn't notice it anyway. Of course, if the other boys' parents knew what they were up to, they'd kill them, so they used to sneak out of their houses when everyone else was asleep and drove to the next town over, where nobody would recognize them.
They had almost been discovered a few times, but they learned from their mistakes and were extremely careful when sneaking out and driving away.

Kyle: Come on, fatass, get in!
Eric: Alright, alright... Hey, why does Kenny always ride in the front?
Kenny: Because I'm awesome like that. Or because Kyle always picks me up first.
Eric: Why is that? Do you guys need to spend some time... alone?
Kyle: No, it's because the next town over is in the opposite direction of Kenny's house. It saves us some time. That's why you're always last.
Stan: Guys, I don't mean to interrupt your discussion with... you know, important things, but can we move? It's Friday night; our parents won't notice if we stay passed out in bed all day tomorrow.
Kyle: Your parents won't notice.
Eric: Well, I said it before and I'll say it again – Your mom is a stupid bi-
Kenny: Cartman, shut the fuck up. I don't want to spend half the trip arguing about this stuff. Let's just go.
Eric: Oh, look, standing up for your boy-
Stan: Cartman, seriously, shut the fuck up. Come on, Kyle, let's go.

Kyle drove away, with Cartman still making snide remarks every once in a while throughout the whole trip, although the other boys ignored him.

They arrived at their usual bar a few minutes later, sat down and ordered some drinks. They talked about things from their childhood, their parents, school; each time preceded by another round of drinks, most of which were drunk by Kenny.

Kyle: So, what do you think everyone else is doing back in South Park?
Kenny: Sleeping.
Stan: Yeah.
Eric: You know, it's getting boring just doing this with you guys. We should throw a party with our friends back in South Park or something.

The other boys looked at each other in disbelief – Cartman had had a good idea for the first time in his life.

Eric: Well? We could use Kenny's house, since his parents don't really give a shit.
Kenny: I do.
Stan: We could just build a sort of club house ourselves. Nobody goes to Stark's Pond anymore, right?
Kyle: Yeah...
Stan: All we have to do is get some construction stuff, call some of our friends and it'll be ready in no time.
Kyle: How much time is "no time"?
Stan: ...Couple of weeks, tops. But it'll be worth it.
Kenny: Who could we even talk to? You do know they'd have to keep it secret, don't you? And what about school?
Eric: There's Butters and... maybe Token?
Kyle: We can talk about this out tomorrow.
Stan: Kyle's right... Shit, it's getting late. We'd better go back before our parents wake up and realize we're missing.
Kenny: We still have time for another round, right?
Kyle: Yeah, if you wanna get left behind. My mom will tear my heart out if she finds out I'm not there.
Kenny: Alright, alright... I get it. Let's go.

The boys payed for their drinks and quickly left the bar.

Kyle dropped everyone off at their houses. First Cartman, then Stan, now Kenny.

Kenny: Thanks for driving us, Kyle.
Kyle: You're welcome.
Kenny: I can't believe Cartman actually had a good idea.
Kyle: It was surprising.
Kenny: Well, I gotta go now. You should go too.
Kyle: Yeah. I'll see you tomorrow, OK?
Kenny: Sure. Good night.

Kyle watched Kenny struggling to walk straight back to his house and, after making sure he made it, drove back to his house, parked the car exactly where it was and went upstairs to his room. He lied down on his bed and started thinking about Cartman's idea.
The more he thought about it the more it seemed impossible. First, who would they get to help them? Butters was terrified of his parents, the girls and the Goth Kids wouldn't help at all... the only kid who could actually help was Token. He could buy the stuff they needed, and he'd probably help them build it too.
There was also the matter of making sure their parents didn't know about it, but since nobody went near Stark's Pond anymore, it was perfect. Kyle eventually fell asleep, imagining what it would look like once it was finished.

A few hours later, the boys' parents woke up and found them sleeping in their beds. They didn't pay much attention to it, though, since it was the weekend.
Stan was the first of the boys to wake up. He glanced over at the clock on his nightstand.

"10 AM... Damn, I've been sleeping for a bit longer than I thought. Well, time to get up."

He got up, trying not to move around too much, and dragged himself to the nearest bathroom.
A few minutes later, Stan remembered Cartman's idea, went back to his room and started writing down his thoughts – Who they could talk to, what the building should look like, etc.

Cartman was the second boy to wake up, just a few minutes after Stan. He noticed the faint smell of breakfast in the air and ran downstairs to get it.

Liane: Oh, hi, Eric. I saw you sleeping, but I didn't want to wake you up.
Eric: Hey, mom. Thanks for that. Where's breakfast?
Liane: It's right over there.
Eric: Thanks.

A few years ago Cartman learned how to be genuinely polite; at least while he was around his mother. He was still a dick to his friends, but they didn't mind. If he started acting nice, then they would be concerned.

Kyle was the third to wake up, one hour after Cartman. Although he didn't drink as much as the other boys, driving in the middle of the night still took a lot out of him. He noticed his brother was using his computer, despite the fact that he had told him dozens of times not to.

Kyle: Ike, get off my computer.
Ike: One sec...
Kyle: Now!
Ike: Alright, alright... I'm going...

"Fucking Ike... Cartman must be glad he doesn't have to deal with this shit."

It was already past 1 PM, but Kenny was still sleeping. He was finally woken up by a phone call. He didn't want to get up, but his ring tone was annoying him. He picked up the phone and saw it was Kyle.

Kenny: Kyle...
Kyle: Sorry, did I wake you up?
Kenny: Kinda.
Kyle: I should call again later.
Kenny: Well, I'm awake now, so go ahead.
Kyle: I just wanted to let you know that we're meeting over at Stan's in about thirty minutes.
Kenny: What for?
Kyle: You know, to talk about the idea Cartman had yesterday.
Kenny: Right.
Kyle: ...Do you want me to pick you up?
Kenny: Thanks, but I'm alright.
Kyle: Alright, I'll see you later then.
Kenny: OK. Bye.

Kenny put his phone down. He didn't hear any noise coming from the rest of the house, which was unusual, but he payed no attention to it and dragged himself to the bathroom.
A few minutes later, when he went downstairs to get some food, he noticed that his parents weren't there.

Kenny: Kevin, where's mom and dad?
Kevin: They went out.

"That explains the lack of noise."

Kenny: ...Wait, did they go together?
Kevin: Yeah. I was surprised too. Hey, why did you only get up now?
Kenny: You know, it's the weekend. I just thought I'd sleep for a couple more hours.
Kevin: It's way past 1 PM.
Kenny: Am I being interrogated here or something?
Kevin: No, no...

"I wonder if Stan has to endure this crap from his sister..."

45 minutes later, the boys had already decided who they were going to talk to. Kyle talked about the idea he came up with before he fell asleep, and everyone else agreed. Stan showed his drawings, which everyone also liked. Now they just had to wait for Kenny to arrive.

Eric: We could just get things ready ourselves and talk to Kenny later.
Kyle: He'll be here. Just give him a little more time.
Eric: I'm not saying we should keep him out of it, we should just try to move things along.
Stan: Cartman's got a point. If we're gonna finish a project like this we need to start now.
Kyle: And waiting a few more minutes is gonna kill you? Seriously, you guys need to learn some patience.
Stan: Fine...

Kenny arrived a few minutes later, just as Stan and Cartman were about to get things started without him.

Kenny: Sorry I'm late, guys. I... lost track of time. So, how is the plan going?
Eric: About damned time! Listen, we're gonna get Token to help us with money for the stuff we need and then we're gonna get Tweek and Butters to help build it.
Kenny: Are you sure Token will help us?
Stan: Of course he will! Token's our friend.
Kenny: Well, if you're sure, we should get started then.
Kyle: Yeah. We'll go talk to Token; Cartman, you can go talk to Tweek and Stan, you go talk to Butters.
Eric: Alright. Let's go. We'll meet later at Stark's Pond.

"No comment about the fact that Kyle and I are going together?"

The boys went their separate ways, talked to the people they had to and regrouped as planned.
The first group to arrive was Cartman's. Butters was really excited to help, so he wanted to hear more about it. Cartman told Butters to calm down, as Stan, Tweek, Kenny, Kyle and Token would be there soon.
Stan and Tweek arrived shortly after. Tweek was as excited as Butters, if not more, but that was his normal state. Stan showed his drafts to Butters, who got even more excited. He immediately started drawing more precise blueprints while they waited for Kenny, Kyle and Token.
Kenny and Kyle arrived almost fifteen minutes afterwards, but Token wasn't with them.

Eric: What took you guys so long? And where's Token?
Kenny: We were trying to convince Token to help us. It wasn't easy, but we did it.
Stan: And where is he?
Kyle: He couldn't come with us. But don't worry, he said yes.
Leopold: That's awesome!

"He's way too excited about this. It's kinda creepy."

Leopold: So, when can we get started?
Kyle: We still have to wait for Token to order the stuff we need, then we have to wait for it to arrive, but we should be done in three weeks. We could work faster, but then our parents would start asking questions.
Leopold: Right... Wait, don't you think our parents will notice large trucks driving into town with construction material?
Kenny: Nah, we told them to take a detour. Nobody will notice.
Eric: Are you ladies gonna chat all day or can we start picking a spot to build on?
Stan: Cartman's right; let's go.

After a long time, the boys finally decided to build on the far side of the lake. They went back into town and to their respective houses, still discussing ideas.

Two weeks later, they had already started building their club house. There was a lot of work that needed to be done, but they already had everything they needed – They had a blueprint, they had all the materials they needed, they had learned how to build something that wouldn't collapse when more than three people stood on it, etc.

Two more weeks went by and the boys had finished building their club house. It had couches, tables, a small "bar area", windows, fire extinguishers (per Kyle's request, just in case), a stereo... the only thing they didn't have was a bathroom, but they were working on it. They even managed to acquire a generator so they could use small appliances.
The boys just stared at it in awe. They couldn't believe they had actually built something like this.

Leopold: This turned out better than I expected.
Stan: No kidding. I can't believe we actually got all this stuff.
Kyle: Token was the one who got everything.
Token: Well, you guys are the ones who built it. I just gave you the things you needed.
Kyle: Still, if you hadn't helped, odds are we wouldn't have been able to build something this awesome. Thanks, Token.
Eric: Now we just need to plan a date and invite people to come here. We should also probably get some more drinks and food.
Kenny: Yeah. Otherwise you'll eat it all and everyone else will be hungry.
Eric: What did you say?
Stan: Come on, guys, chill.
Tweek: W-Who should w-we invite?
Leopold: What about Jimmy? He's cool.
Eric: Or...

The boys discussed for a very long time before coming up with the list of guests – Jimmy, Timmy, Craig (much to Cartman's disapproval) and Clyde. Although that was a short list, along with the boys that would be eleven people, which they figured was enough. They sent short invitations to their friends and waited for the big day.

That's the first chapter. It's basically a highlight of their friendship. The entire story will be four chapters long. I will start the second chapter later today.