Virgin Mobile USA is at it again, this time releasing a new, slightly off-the-beaten path marketing campaign that features “Sparah” and a cameo by Sir Richard Branson, founder of Virgin Group.

With “Sparah,” Virgin Mobile is manufacturing a celebrity couple featuring Spencer Falls and Sarah Carroll. Launched yesterday, the campaign invites customers to “Keep Up with Sparah” at www.facebook.com/virginmobilelive. Of course, Virgin Mobile customers are encouraged to follow the couple on their Android-powered phones – and unlimited plans starting at $25/month.

Apparently, the Sprint-owned prepaid unit plans to keep this campaign going longer than some real-life (or real-life photo opp) celebrity match-ups. Over the next six months, Spencer and Sarah – two strangers selected from a casting call of thousands – will appear in the integrated marketing campaign that includes national TV commercials, print and a series of digital webisodes chronicling the couple’s rise to fame.

As part of their contract with Virgin Mobile, the couple is required to chronicle their journey across a host of social media channels, including Facebook, Twitter, Foursquare and video blogs.

They’re pulling out all the stops. Virgin Mobile says “Sparah” will be equipped with a house in the Hollywood Hills, a stylist and a publicist, all furnished by Virgin Mobile, to ensure they reflect all the trappings of a real celebrity couple. As their fame grows, the couple will be asked to participate in activities typical of A-list product endorsers, including photo shoots, TV commercials, store openings and appearances at signature events, such as Virgin Mobile’s annual FreeFest music festival.

Branson’s cameo in the ads marks a first for Virgin Mobile. “Virgin Mobile’s unlimited Web and data plans are really taking off with people using them to follow celebrities and pop culture,” Sir Branson is quoted as saying in a press release. “Virgin Mobile likes to give people what they want. And in this spirit, I know they’ll use all of their resources to create a legitimate celebrity couple to ensure their customers never run out of something to tweet about.”

Sprint, which acquired Virgin Mobile USA in 2009, added 846,000 net prepaid subscribers in the first quarter of 2011; that figure includes net additions of 1.4 million prepaid CDMA customers offset by net losses of 560,000 prepaid iDEN customers.