This won't be the first time he's done so; Franco has already appeared as James Franco in 30 Rock, This Is The End and Richard Peter Johnson (that one hasn't come out yet). He'll presumably play a minor role, along with Live Free or Die Hard star Justin Long, who reportedly already shot scenes with the film's stars.
Here's what Zap2It had to say about Franco's role:
He'll be one of several celebrities in the movie who have been victims of a hidden camera scam. No, not like on "Duped!" -- "one of those reality shows where people get duped into doing stupid things like giving some stranger their car or a bunch of money."The film, which raised $5.7 million from more than 90,000 backers on Kickstarter, is set to have a limited theatrical release and then go to home video in February and March 2014. Depending on its reception, the filmmakers have hinted that the characters could have more adventures down the line--and one that's confirmed is a Hall H presentation at Comic-Con later this month.
But the kind of scam where someone hides cameras in famous people's houses and tries to sell the videos. Sounds like a case for everyone's favorite pint-sized private eye.