This Week's Cover: The Surprising Power of 'Pretty Little Liars'

Television isn’t just about ratings anymore. Now networks are fighting to earn the “most social” title for their hit shows, and one of the savviest series in the social media universe is the over-the-top teen mystery Pretty Little Liars. The ABC Family phenomenon and its digitally-inclined stars — Lucy Hale, 23; Ashley Benson, 23; Shay Mitchell, 25; and Troian Bellisario, 27 — are changing how networks measure success, one photobomb, tweet, status update, and Keek video at a time.

Some of the of their posts may be related to the ABC Family drama, where the girls play an atypically glamorous high school foursome tormented by anonymous and cunning cyberbullies out to punish the friends of a dead queen bee. But the cast’s real gift is for unleashing more personal-flavored details — a video of Benson slinking around to Justin Bieber’s “Boyfriend” with person-of-interest James Franco; photos of Hale in the studio recording her country album — that serve as a dose of gossip-crack for viewers and fans, which keeps them clicking and tuning in. Pretty Little Liars draws 3.8 million viewers each week, while also maintaining a colossal digital footprint of more than 10 million likes on Facebook, a Twitter handle (@ABCFpll) with a million-plus followers, and four stars who collectively reach more than 5.5 million with a tweet or retweet. (Hale alone boasts 2.2 million Twitter followers.)

Just in time for Social Media Week — going on right now in NYC — EW explores how Pretty Little Liars cracked the social-media code, and how other series hope to learn from their success. Plus we get the cast and exec producer I. Marlene King to preview the remaining episodes — Emily becomes a detective! Spencer goes crazy! “Red Coat” will be revealed! — as PLL heads to its third season finale on March 19.

For more on Pretty Little Liars and the social-media phenomenon around it, pick up the new issue of Entertainment Weekly, on stands February 22.