Occasionally, cinema gives birth to twins. The year 1998 saw two extemporary but radically divergent takes on World War II: “Saving Private Ryan” and “The Thin Red Line.”

In 2005, “Munich” and “Paradise Now” fit together like two interlocking pieces of the same puzzle. And now, in 2010, “The Social Network” and the documentary “Catfish” have been released just days apart, each an examination of the online experience and how we go about maintaining and fostering relationships in the digital age.

It is almost impossible to write a review, much less a synopsis, of “Catfish.” Since the film works as one big reveal, the less you know going in, the better. All you need know is that the doc follows Nev, a young photographer from New York City, and his increasingly peculiar online relationship with a family in rural Michigan.

When Nev decides to drive out to Michigan and meet the family in person, he discovers not everything is what it seems.

“Catfish,” which had its world premiere at the 2010 Sundance Film Festival, purports to be completely authentic. But we live in a post-James Frey, post-“I’m Still Here” hoax-umentary world. So it should come as no surprise that more than halfway through the film, I wrote in my notes: “I don’t, for a minute, believe this movie is real, but it helps to pretend it is.” It is much more enjoyable to be carried away by something you believe is true. But just minutes later, I jotted down a contradictory entry: “Wowsers, I think this IS real.”

Whether “Catfish” is 100 percent completely honest (I believe it is not fiction, but I do not believe it is wholly genuine) is ultimately irrelevant. Real or not, it leaves quite an impression, a pervasive, almost Alex Jonas paranoia. And trust me, you will be arguing about this film from the parking lot to the water cooler many days later.

“Catfish” will shake you to your Internet-surfing core — not because it starts to feel like a horror film halfway through, but because it does not end like one. “Catfish” is a commentary on love and identity as filtered through a giant, Hitchcockian cyber-colander. It forces us to confront the illusion of intimacy created by the Internet, as well as the ease with which we are able to fabricate and misrepresent our true selves.

CATFISH

Cast: Yaniv “Nev” Schulman

Directors: Ariel Schulman and Henry Joost

Rated: PG-13 (for some sexual references)

Running time: 1 hour, 34 minutes

GRADE: A-

Photo by Still of Yaniv Schulman in Catfish