Tinseltown has invaded Facebook.
In News Feeds across the massive social networking site, glam shots of the red-carpet ready have replaced familiar photos of family and friends as Facebook fans by the thousands join in on the latest fad to sweep the site.
"It's Doppelganger Week on Facebook," according to messages posted on countless member pages. "Change your profile picture to someone famous (actor, musician, athlete, etc.) you have been told you look like. After you update your profile with your twin or switched at birth photo then cut/paste this to your status."
Though the earliest posts started appearing last week, for those only getting the memo now, "Doppelganger Week" is just beginning.
Bryn Haffey, a 26-year-old lawyer in New York, changed her profile picture to that of Anna Chlumsky's (of "My Girl" fame) a few days ago when she saw images of singer Matisyahu, reality star Kim Kardashian and actor Elijah Wood populate her Facebook page.
But she said her second Kim Kardashian "friend" didn't emerge until today.
"It's one of the few Facebook activities that everyone can join. ... It's really quick and easy and it's fun," she said. "I think it's a way to express yourself, but then also see how your friends would express themselves to the same inquiry."
Though other fads have made the rounds on Facebook, such as last year's sensational "25 Personal Things About Me" and the recent bra color status updates, for some, the doppelganger trend is a way to relate to the greater community without revealing too much.
"It's a no strings, fun, little activity," explained 30-year-old Heather Stone of New York, who said she usually passes over the more personal fads to come through Facebook.
She said a woman who works at her gym once mistook her for actress Alicia Witt, who starred in "Mr. Holland's Opus," so choosing her doppelganger was an easy task.
For most Doppelganger Week celebrants, the trick was finding a celebrity whom they resembled on the outside. But for some, it was about choosing the star whom they resembled on the inside.
"The first thing that popped in my head was Animal from Jim Henson's Muppets," said Micah Pruett, a 26-year-old graphic designer from Kahoka, Mo. "He kind of fits my personality. ... Like a party animal."
Madhu Soma, 26, of New York, wasn't even on Facebook when he was prompted to post his celebrity likeness.
He said he was in line at a Dunkin Donuts, checking out Facebook on his iPhone, when the woman behind him said, "Did you pick your Doppelganger? You should."
She said she'd chosen actress Kristin Bell (who starred in "Forgetting Sarah Marshall") and suggested he choose Sendhil Ramamurthy, who plays Dr. Mohinder Suresh on NBC's "Heroes." So he did.
"People need new things to do on Facebook," he said. As people continue to send links, circulate pictures and post messages, the site runs the risk of getting stale, but "this is something different," he added.
But despite the reach of Doppelganger Week, its origin appears to be a mystery.
In a piece for the Huffington Post, Alex Grossman transcribed an "Interview With Bob Patel, Creator of 'Doppelganger Week' on Facebook."
"It all started when the guys at work started teasing me that I look like Tom Selleck," "Patel" said. "They're like, 'Hey, Tom Selleck, what are you doing?' Or, 'Yo, Tom Selleck, we're talking to you.'"
But later in the comments section, Grossman sarcastically reveals Patel's true nature.
"More than a few people have questioned whether this interview and Bob Patel are real," he wrote. "Bob Patel is absolutely real. He lives across the street from Santa Claus, just around the corner from The Easter Bunny. Geez..."
In an e-mail, a Facebook spokeswoman said the site doesn't have the ability to track the origin or spread of trends like the Doppelganger pictures.
"Anecdotally, these types of things seem to start with one person or group of people ... and then spread rapidly through the social graph because of products like News Feed," she said. "By the time we recognize the trend, it's usually difficult to pinpoint the exact beginning."
And though many have joined the fun, some are already taking part in the protest.
The "Thanks to Doppelganger Week I Recognize Narcissists Right Away" group counts more than 200 people among its members.
And Kristy Korcz, associate editor of the blog GeekSugar, said that when her site asked users if they took part in the latest Facebook "theme weeks," most said "no."
She said this one seems particularly popular because so many people are caught up in celebrity gossip, especially during awards season, but the people who are participating in Doppelganger Week appear to be those Facebook users prone to status updates and frequent postings.
"The majority of users are saying I don't participate," she said about her blog's readers. "They use it to keep in touch with friends and family and don't want to play games."
Some, she said, are so done with the constant march of Facebook trends that they want them to stop.
But amusement or annoyance, Justin Smith, editor of the blog Inside Facebook, said the Doppelganger trend and other similar fads are likely here to stay.
"In many ways, what we're seeing is that some of these Facebook phenomena are replacing the old chain letters that our parents used to send," he said, adding that the social, connected nature of Facebook makes it easier than ever for information and applications to spread virally.
As more people join the site, he said he predicts the trend will only continue.
"I would expect to see more of these things," he said. "More fads spreading quickly."