This problem is probably more common in some random way than it seems, but here it is:
I live on campus in one of the school's townhouses. My dorm mates and I (eight of us counting the two RAs) share our porch with a bunch of boys (same ratio). Two of them have girlfriends—that we know of. While some of the girls are more interested in dating them than anything else, most of us just want to get to know them. As friends. They are our porchmates after all. But they pretty much avoid everyone. There's one of them—out of EIGHT—who regularly comes out of the house to social events. I've talked to seven of them, and they're really sweet and don't seem to think that I'm a crazy homicidal boy hunter. I have absolutely no clue why they're constantly hiding out. Is there any way to like, get them to socialize?
PS: I love your advice column! It's the funniest, most blatantly honest thing I've read in a while. Keep it up!
Let me start by assuring you that these guys are interested in hanging out with you and your dormmates. The number one rule of human boyness is that, if you see a human girl, you beeline directly for it and attempt to make out, even if this means running into traffic or scaling a large building. But wanting to socialize and actually doing it are, at least for some guys, very different tings. They're going to have to feel comfortable around you and your friends first.
Example time: freshman year, I went to what I am absolutely sure was one of the country's nerdiest schools. For a reaction quote in the school paper on the subject of campus safety, one kid rambled on about how true safety revolves around the code of the samurai. The closest I ever got to a party with dancing was when I signed up for a tango class and my very first partner was, out of sheer blind stupid luck, my ex-girlfriend. I lived in a suite with five other guys, some of whom would converse with IMs even though they lived in the same room and were sitting three feet apart. There were girls somewhere in our building, probably, but we were less likely to seek them out than we were to be struck by falling space debris. We would have been interested, sure, but 90% of the campus was so used to being insular and weird that they didn't really know where to begin.
If your dudes had no such social hangups, I think they'd already have tried to approach you, so your task now is to try to get them involved without giving them the wrong impression. Frankly, this is not easy to do. The vaguest hint of girlishness has a way of making guys lose all perspective and tact. For example, I know that this is a purely friendly invitation, but if you just go "We are planning an awesome party, you should all come over! Giggle! Titter!" and they do, and your place is strewn with, like... bras, then they're going to get the wrong impression and assume that every single one of you is romantically interested in every single one of them. I realize you probably don't spend your day flinging underwear around with wild abandon; I'm just saying you need to make it clear this isn't that kind of invitation. If a college girl approaches a college boy for any reason except that he is on fire, he's probably going to assume that the unspoken subtext is "let's make out let's make out let's make out."
With all of that in mind, here are my suggestions:
"Are you guys hungry? We should all get lunch!"
Every campus is different, so I'm not sure if you folks all go to dining halls in large groups, but this would be my first suggestion, as even the most secretive shut-ins at my Awkward Nerd Univeristy did it. It's very normal, and it's very clearly a non-romantic invitation. Nobody will expect the outing to devolve into passionate makeouts over the steam tray of moldering hot dogs. Everyone will realize it's just neighbors trying to be friends, and once everyone's more comfortable around each other, it opens the door to doing things in the future that are actually fun.
"Let's all go to the Daytime Sporting Event!"
Do not actually call it the Daytime Sporting Event. If you're lucky enough to have a popular sport that's in season, this is a nice, friendly context for hanging out with people you don't know well. If your school athletics leave very much to be desired, and all you have is the Division III Wallyball Qualifiers, held in an abandoned parking lot, then it's okay to skip this approach.
"You guys should all come over because (flimsy excuse)!"
Do not actually say "flimsy excuse." Instead, substitute any old pretext for hanging out—watching some season finale on TV, or a movie, or just because you made some food and need some humans to help you eat it. As long as the place isn't bedecked with bras, they won't misunderstand your intentions.
Just be up front about it.
Of course, you could always just tell them pretty much the same words that you wrote to me. "Hey, you guys live right next door, so we should hang out sometime" is pretty clear and straightforward. You might approach the one guy who is social, and get him to badger his roommates into poking their heads out out into the sunlight once in a while; he might have better success convincing his friends than you will. I don't think these guys realize that they are, in your words, hiding out—I think they're just doing their thing (which, let's be honest, is almost certainly MMOs) and not realizing that anybody else is actually interested in talking to them, and if you make that clear, I think they'll be happy for the chance to socialize.