Ricky Gervais and Emily Blunt have signed up for cameo roles in the forthcoming 'Muppets' movie.

The British stars will appear alongside a Hollywood-heavy cast including Jack Black, Jean-Claude Van Damme, Zack Galifinakis and Billy Crystal in the James Bobin-directed project, which sees Kermit, Miss Piggy and co putting on a show in order to help save their movie studio from an evil developer who wants to destroy it.

Jason Segal is taking the human lead in the film - which he wrote with Nicholas Stoller - with Amy Adams and Chris Cooper also taking key roles.

It is not known what roles Gervais and Blunt will play, according to The Hollywood Reporter.

It was previously reported 'Glee' actress Jane Lynch was joining the comedy movie, but she has since denied being approached.

The movie, which has yet to be officially titled, is the first 'Muppets' movie since 'Muppets from Space' in 1999 and is due for release in December 2011.