shaquille o'nealSocial TV startup Philo tells me user numbers are “through the roof” right now, thanks in large part to copying a strategy from traditional TV — bring in the stars.

What kind of stars? Well, basketball star Shaquille O’Neal, for one. Philo hosted one of its “virtual viewing parties” for the NBA’s Sprite Slam Dunk Contest this weekend, where O’Neal posted play-by-play comments on the contest while viewers could check-in and interact on the Philo website, its smartphone apps, or a Philo widget hosted on the website.

When Philo told me about the promotion, I noted that the company had announced a number of similar partnerships over the last few months — including official viewing parties for Spike’s Video Game Awards, AMC’s The Walking Dead, and BBC America’s Doctor Who. So I wondered: Do these promotions actually pay off in increased user numbers?

Here’s what a company spokesperson told me:

User numbers are through the roof right [now] on Philo, and each of our partners is benefiting from an engaged and socially active audience. We completed a recent partnerships with AMC around THE WALKING DEAD, where a cast member chatted live on Philo with fans during an episode. This generated millions [of] real-time Facebook profile updates for the network, and we’re seeing similar numbers across the board.

All of our promotions with networks and online destinations have been huge successes, with each of our viewing parties producing millions of real-time Facebook profile updates during one episode of a show.

The most successful promotions, like The Walking Dead one, involve interactions with a star from the show, as well as some kind of real-world prize, the spokesperson told me.

Philo isn’t the only social TV company to experiment with these kinds of promotions. Miso, for example, has announced a number of show partnerships, including one with the Oprah Winfrey Network. (Disclosure: Miso investor Georges Harik is also an investor in VentureBeat.) But Philo is the only one I’ve heard of that’s incorporated this kind of behind-the-scenes chat with stars.

Of course, you can already find many of those stars on social networks like Facebook and Twitter, which are an increasingly important way for TV shows to interact with their fans. (In fact, one of the main ways Philo said it would promote the chat was by having O’Neal tweet about it.) Apps like Philo don’t have the same reach, but they do allow stars and networks to reach the specific audience that’s watching a show at the moment it’s being aired.

New York-based Philo has raised an undisclosed amount of funding from North Bridge Venture Partners, DFJ Gotham Ventures, Eniac Ventures, and TV producer Stephen Lambert.