For Amitabh Bachchan, each project comes with its own challenges, and his latest "Gulabo Sitabo" was no less. "Each film project is a challenge for those that agree to work on it. GiBoSiBo (the short name by which the film is being promoted) was no less," Amitabh told IANS while talking about the biggest challenges he faced while working on the Shoojit film.