There’s incredible (and welcome) cultural whiplash in sneaking away from the middle of the determinedly highbrow New York Film Festival to head to Austin for Fantastic Fest, an event that’s most certainly not. Dedicated to horror, sci-fi, fantasy, cult and general genre fare, Fantastic Fest is the brainchild of Alamo Drafthouse founder Tim League with support from Ain’t It Cool News‘ Harry Knowles, with a line-up of international fanboy sprawl that this year includes everything from Icelandic LARPing comedy “Astropia” to Korean Leone homage “The Good, The Bad and The Weird” to a documentary about William Castle and sidebars focused on Ozsploitation and Japan’s softcore pinku films.

Fantastic Fest has become famous for TBD secret screenings that have turned out to be some kickass gets for such a young event — an unfinished version of “Apocalypto” with Mel Gibson in tow as well as the world premieres of “There Will Be Blood” and the final version of “Southland Tales.” But its standout quality remains that it’s such a rowdy, jovial and mind-blowingly unceremonious good time, with filmmakers, talent and fans milling around the strip mall-centered headquarters, sipping pints of Shiner Bock during the screenings and taking off for excursions to eat BBQ and shoot skeet.

The opening night film, the U.S. premiere of Kevin Smith’s “Zack and Miri Make a Porno,” kicked off with an Alamo Drafthouse standard vintage trailer for the ridiculous 1987 Hong Kong film “Thunder Cops,” followed by festival director League, in a monk robe, gonging in the “spokesperson for the disenfranchised, genre-loving generation” to introduce his flick. It’s not as true as it used to be — Smith, with his lingering “Star Wars” devotion and his (yeah, really funny) stories about cracking a video store toilet with his ever-expanding girth, isn’t so exemplary of a crowd that’s getting to be geeky-hip, pierced and tattooed and possessed of a smattering of self-taught Japanese. Still, the film went over like gangbusters, as it’s probably going to go over with any crowd, an on-the-surface raunchy romantic comedy with a marshmallow-soft heart that brings Smith’s career into the Judd Apatow era. Apatow muse Seth Rogen plays a Pittsburgh coffee shop slacker who’s lived for the past post-high school decade with his childhood gal pal (Elizabeth Banks), who’s equally charming, underachieving and underemployed. Of course, there’s never been a hint of sexual tension until the two, in tough financial straits, decide to recruit friends to make an amateur porno and discover that neither actually wants to see the other have sex with anyone else. nderneath the cartoonish sex, scatological humor and no-inner-censor dialogue, “Zack and Miri”‘s a traditionally arced love story in which a man and a woman who are obviously meant to be together are kept apart for a while by plot devices and lousy communication. But Rogen and Banks are luminously likable and alchemical together, convincingly comfortable and closer than family even before they start to see each other in a different light.

The DIY porn shoot scenes themselves have a kind of delighted dirty innocence that makes “Zack and Miri” a not-quite-NC-17 cousin to “Son of Rambow,” with Traci Lords, Craig Robinson and Smith’s beloved Jason Mewes and Jeff Anderson among the ragtag group that gathers to fuck and film it all while wrestling with booms made from microphones taped to hockey sticks and an in-scene soundtrack playing on a tape deck next to the camera. Smith’s earliest films may have been made in similar conditions, but he’s come a long way since then, both in production value and in sentiment. “Zack and Miri” may be, like many recent rom-coms, a film with characters who’ve seemed to have avoided self-examination all of their lives, but it’s also guiltily, endearingly sweet despite all of the attempts to cut the syrup with anal sex jokes. Smith, you big softy.

Immediately post “Zack and Miri” were the Air Sex World Championships. Air sex is air guitar except, you know, with sex. No description could do it justice, but below are three blurry photos to give you a hint