After the surprise success of The Muppets in 2011, first-time British director James Bobin knew making a sequel would present a big challenge. "I thought we needed to make it harder," he says. "So that's what we did: let's make an action comedy musical movie, you know!"

The MuppetsRicky Gervais in The Muppets Most Wanted

The movie sees the Muppets embark on an ambitious world tour, taking in Berlin, Madrid, Dublin and London while a nefarious plot unravels around them. As expected, the story is plainly ridiculous, and merely exists to let the Muppets indulge in all kinds of craziness. It also allows for some terrific human actors to join in the fun, including main cast members Ricky Gervais, Tina Fey and Ty Burrell and a blinding array of cameos from Celine Dion to Tom Hiddleston.

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When writing the script, Bobin says he often includes names of people he'd like to have in the movie. "Like you can't do the Christoph Waltz joke with anybody else," he says, "because it's about a waltz!" Fortunately, Waltz turned out to be a fan. And Bobin adds, "A lot of people just approach me on the streets asking to be in the movie. One of them was Lady Gaga."

Bobin feels that the Muppets have an important place in entertainment history. But the producers will wait until they see how audiences react to Muppets Most Wanted before deciding on what to do for a possible sequel.

Watch The Muppets Most Wanted trailer: