What's mine is mine and what's yours is mine

Life is a series of obsessions. Some are impulsive and fleeting, like Swatch watches, while others are deep-rooted and last a lifetime, like not trying not to die. Often, these obsessions are shared with those with whom we spend a lot of time. Such is the case at work where many of us are currently obsessed with "It's Always Sunny In Philadelphia", the FX sitcom about a group of people on a quest to demonstrate the absolute worst manners, morals, and judgement in television history. In our office, the show is mentioned several times every day, whether somebody is quoting dialogue or reliving scenes from a favorite episode.
Yesterday, Billy went on the shows official website and downloaded an icon of Charlie for use on his Yahoo! messenger. I decided it was pretty cool looking so I went and downloaded it for my Yahoo! messenger too. Billy was not amused...

BILLY: Man, don't do that. I already have Charlie.
ME: I know. I want Charlie too.
BILLY: Well, we can't both have Charlie. That's stupid.
ME: Ok, take somebody else. You can have Sweet Dee.
BILLY: I don't want Sweet Dee.
ME: So get Frank. Frank is hilarious!
BILLY: I don't want Frank, Sweet Dee, Dennis or Mac. Charlie is mine. I had it first.
ME: You can't claim Charlie as yours. It's on the internet, free for anybody who wants it. And I want it.
BILLY: That's fucked up. I can't believe you're stealing my shit.
ME: It's not stealing. It's free from the FX network.
BILLY: You only want it because I have it!
ME: That is almost entirely true. But so what? It's not like you can do anything about it.
BILLY: You know what? Go ahead and keep Charlie. I don't care. I'm going to get a different one. But please don't copy me and steal that one, ok?
ME: Sorry, I can't make that promise. Actually, I'm already a little bored with Charlie and if I see something else I like better, I may change it.
BILLY: I hate you!
ME: Ha ha ha!
BILLY: Do you remember the other day when I stabbed your foot with that umbrella? I apologized and said it was an accident. Well, it wasn't an accident. I did it on purpose. I knew you were going to steal my shit so I went back in time and stabbed your ass in the foot. And I'm glad I did it too!!
ME: None of that makes any sense. It's obvious that you have no familiarity with the concepts of time travel or human anatomy. Therefore, you have demonstrated that you do not deserve cool chat icons. So go see if you can download a Liam McPoyle chat icon. Because you suck.
BILLY: GOD, I HATE YOU SO MUCH!!!
ME: Ha ha ha ha ha!!