Even for those who enjoy sci-fi, you’d have to be a very big fan — or very easily amused — to relish the idea of sitting through 24 hours of the stuff. I, for one, approach the Coolidge, on a frigid, dreary Sunday afternoon, with something approaching panic. My backside aches at the very thought of squirming in a movie chair for the equivalent of 12 — 12 — feature-length movies. My stomach churns in anticipation of the crap it’ll be asked to digest (by the time I leave the theater, I’ll have consumed a gallon of Diet Coke, a double cheeseburger, a large fries, a chicken sandwich, another cheeseburger, a slice of pizza, a bag of Skittles, and a chicken burrito — the latter at six in the morning.)

Then there are the movies. Before I enter the theater, I scan the program. The final film — screening at 10:10 a.m. tomorrow — is Equilibrium: " In the future where freedom is outlawed, outlaws will become heroes. " As I stand staring at this sentence, I become aware of people passing by: Marathoids! It’s actually a bit of a disappointment. While none of them is likely to make the cover of Vogue, they don’t look that geeky. There are many pairs of spectacles, pell-mell hairdos, and rumpled winter jackets, all blended in such a way as to suggest high intelligence — as if the entire MIT community had turned out for the event. The most remarkable thing about the crowd, though, is how happy everyone looks. I have to suppress the urge to seize their pin-heavy lapels and say, " Do you know what you’re letting yourselves in for? "

They do.

For those who come here year after year, the " sweet torture, the delicious pain, " is all part of the allure. It’s an ordeal — a " survival ritual, " as " Major " Tom Chenelle, the 46-year-old Commander of the Martian Liberation Organization, puts it. The marathon gives these sci-fi buffs not only a chance to immerse themselves in the movies they love, but also a chance to prove their devotion to the genre, and their mettle. " There is definitely a sense of accomplishment, " says Schwartz. " It’s almost like a vision quest — you’re pushing yourself, but not for enlightenment, just for the sake of doing it. "

Robert Viagas, for his part, likens the sci-fi marathon to the other Boston Marathon — " except you get to sit down. " Viagas goes on to point out that the marathon’s official slogan is " Old enough to know better, young enough to stay awake. " It’s a good slogan, but not a particularly accurate one — after nearly 30 years, the majority of the Marathoids are not exactly fresh-faced youths. " The hard part is between 3 and 6 a.m., " Viagas says. " Staying awake for those three hours separates the men from the old men. "

Even more important than surviving the marathon — or at least staying awake through it — is doing so together. " We’re like a platoon of soldiers trudging through the mud, " says Suzzanne Ochoa. " There’s an odd pleasure about that. You feel it, you feel it. " Which brings us to another important aspect of the event. Speak to any regular and you’ll hear the word " community. " They’ll talk of friendships forged, of watching each other grow up and grow old, of kids being born, parents passing away. The majority of these people see each other only once a year, but they’ve been doing so for the better part of three decades. " It’s like Brigadoon, " says Garen Daly. " Every year this little town of 600 people emerges. "

Within seconds of the opening credits, you get a clear sense of this familiarity. It also becomes apparent that the entertainment relies as much on what’s going on in the theater — the catcalls, the in-jokes, the witticisms — as what’s happening on the screen. Sometimes it’s specific, improvised, as when a character addresses a miniature horse — " Hey little fella, where did you come from? " — and someone barks out, " Answer me! " At other times, the interactions have as much to do with nostalgia as with wit. In a film they’ve all seen a million times, people shout, " Mark! " every time someone on screen says the name (60 times: someone counted). And whenever a military figure appears in any film, everyone growls — Grrrr! — harking back to a comically grumpy general from a terrible movie many years ago.

This kind of audience participation has caused some friction among the festival crowd, with the purists demanding that the hoots and heckles be kept to a minimum — so this year, according to regulars, is a relatively subdued one. You wouldn’t know it. At one point, a figure on the screen starts whistling, and the entire theater whistles along, tunelessly, endlessly. When a tyrannosaurus is felled, someone yells, " No dinosaurs were hurt during the making of this movie! " And then there are the ray guns, which spark and squawk throughout.

If this sounds silly, it is. Most of the festival faithful don’t mind being called dorky — they regard the wrinkled noses and dismissive huffs they get as a sign of other people’s limitations, not theirs.

Dorky or not, there is at least something childlike — or childish — about SF/28, and this, too, is part of the attraction. Garen Daly likens his annual Close Encounter of the 24-Hour Kind to traveling in time. " I climb into my Way-Back Machine and take myself back to when I was 12 or 13, " he says, " that innocence, that sense that anything is possible. "

There is a generation of people who can still recall hollering, " Behind you! " during Saturday-morning cinema, who grew up in an age of clunky special effects and clunkier dialogue. Though Steven Spielberg’s Minority Report is on the schedule for SF/28, it’s films like The Invisible Boy that are the marathon’s bread and butter. " I grew up in the late ’50s watching the big-bug movies, " says Ed Symkus, 52, senior arts writer at the TAB newspapers and a 21-year veteran of the marathon. " I went to see these films every Saturday at the Franklin Park Theater in Dorchester. When I go to the festival, I’m back at the Franklin Park. " He adds, " There’s something wrong with me. I refuse to grow up. "

Actually, there probably isn’t anything wrong with Symkus. The marathon may be an extreme form of escapism, but so are skiing and binge drinking. Everyone, after all, needs to get away from it all once in a while — and what better way to do so than drifting off to The Planet of the Vampires or spending a couple of hours with the Invaders From Mars? As Robert Viagas puts it, " The Neverland of the Marathon allows a brief respite from the pressures of adulthood, fatherhood, and the real world. "

As it happens, I am also a part of the Saturday-morning-cinema generation, and it starts to show. By midnight, despite my previous reservations, I actually start laughing at the dinosaur gags. I yell, " Mark! " when everyone else does. I even enjoy the awful Sh! Octopus, if only because I am aware that the people around me are just as mortified as I am. But it’s not easy. My constitution is suffering from the constant barrage of junk food, my back feels like someone dropped a refrigerator on it, and my ass seems no longer with me — but all this will only make my war stories better later on. It seems absurd to say so, but when noon finally rolls around, when the doors open and the crowd disperses into a thickening blizzard, I am very close to being disappointed. Perhaps it’s the lack of sleep.

I’m not sure whether I’ll be back for SF/29. It’d be interesting to see whether the chant " Stomp those grapes! Stomp those grapes! " — taken from a toe-curling bacchanal in one of this year’s films — will make it through to next year. And I’d like to see some of the people again. But, you know, 24 hours. Anyway, there’s an outside chance the festival won’t even be around next year. As Garen Daly says, running the event is " not real lucrative. " He can’t keep this up forever. " Don’t even say that, " says one regular. " I would have to take my own life if it came to that. Or move to another planet. "

Chris Wright can be reached at cwright[a]phx.com