Jason Segal was "surprised" at how "labour-intensive" working on 'The Muppets' was.

The 31-year-old star - who appears alongside Amy Adams as one of the main human characters in the forthcoming film with Miss Piggy and Kermit - admits he did not expect to see the large amount of uncredited work which is down by puppet-masters behind the scenes on the movie.

He said: " I think the biggest surprise with working with the Muppets was seeing how labour-intensive it is, working with these puppeteers. Because part of their job, specifically, is to be invisible.

"By the time the movie comes out, you're not even supposed to be thinking that there's a puppeteer operating this. That's just Kermit. And, in reality, these guys are puppeteers, and they're actors, and writers and contortionists, and singers, and they don't get the credit they're due to get because intrinsically their job is to disappear."

In addition to appearing in the movie, Jason also wrote The Script, and he confesses it took time to get executives on board to do the project because it has so many fans who might not be pleased with the result.

He told TheVine.com: "It was a long process. I mean, there's a lot of people who love the Muppets. And so to get everyone who loved and respected the Muppets so much to come to a consensus - a consensus about what was good in order to honour this legacy - it took a long time, but we definitely got there.