Ray Richmond is contributing to Deadline’s TCA coverage.

One of the better kept secrets in cable television is the fact that ABC Family‘s Pretty Little Liars remains something of a phenomenon. Besides being the network’s top-rated series of all time in key demos, it also ranked as cable TV’s top-ranked series of last summer. It’s been renewed for a fourth season that’s skedded to start airing next summer. And during a TCA panel this morning, it came up that one of the reasons for PLL‘s continued audience strength is its pioneering use of social media, generating a major boost from Twitter and Facebook in particular. Exec producer and co-showrunner I. Marlene King noted, “We work very closely with (ABC’s digital and online team). They’ve been amazingly supportive, and we partner on ideas and social media programs with them all the time.” Exec producer Oliver Goldstick concurs. “It almost takes us back to old-time television where we all watch at the same time, because they’re not just DVR-ing and watching it later. There’s an aspect of this that’s truly old fashioned, as cutting edge as it is, because people are experiencing it simultaneously.” That communal viewing experience extends to teenage viewing parties, as King shared with an anecdote this morning. “A woman called the day after the revelation that Toby (Keegan Allen) was on the A Team who asked to speak to the head of television,” she recalled. “She said she still had eight 16-year-olds at her house from a slumber party the night before, and they were still crying.” Quipped Goldstick: “It’s all about bringing trauma to people.”

The producers were also asked how long the series can realistically run given the evolution of the Pretty Little Liars into “Pretty Medium-Sized Liars.” Replied Goldstick: “Time moves very slowly in this town, so their senior year is going to last a long time…They’re going to (ultimately) be Golden Girls Liars.”