LONDON, England (CNN) -- The most eagerly anticipated animated film this year hits big screens this weekend, as "The Simpsons Movie" opens worldwide. The Screening Room spoke to creator Matt Groening and writer Al Jean in London about everyone's favorite two-dimensional yellow family. Simpsons supremo Matt Groening with his creations at the film's premiere in Springfield, Vermont Matt Groening told the Screening Room that fans had driven the demand for the movie. "We've had fans clamoring for a movie for the past 18 years," he said. The film has taken four years to come to fruition, as writer Al Jean explained. "What really held us up for a long time was to have enough people to do the show and the movie," he said. "We talked for a while about doing the movie after the show is done, but the show is never done! So it really started in earnest in 2003, when we started working on this story that became the movie." Technology has also played its part. Jean continued, "The technology to do this film really wasn't even around five years ago. For example, there was this joke I once pitched and David Silverman, the director, started drawing and as I was pitching it, it went into the film and it was cut a day later. To go from pitch to cut in two days is pretty impressive." Its creators hope that "The Simpsons Movie" will both satisfy long-term fans and bring Homer and Marge's family to a new audience. Groening told the Screening Room, "This movie is designed to both honor the people who have loved the show all this time, so there's lots of little details for them in the movie, little characters and stuff who they know and love, but we also want people who don't know the family to not be completely confused. It is a complete movie experience, but again, we have a lot of little details that only the really, true die-hard fans are going to get." And fans can expect to be entertained by plenty of cartoon mishaps. Groening said, "When you see somebody fall off the roof in a live-action film, it's funny -- we all love it. But it's not as funny as when Homer falls off the roof.

In what year did "The Simpsons Movie" come to fruition?

Relying on an animal to come by is risky. A flower may have to wait a long time for the right animals to come by. What if one never passes close enough to the flower? Hoping the wind will blow is also risky for a plant. What if the wind does not blow? What if the blowing pollen does not land on another flower? The wind could even blow the pollen over the ocean where it is wasted. Giving free nectar is costly. It is not a good use of the plants energy. A plant uses a lot of energy to produce nectar. Some animals may just drink the nectar. They may not carry off any pollen in return. To improve their chances, plants evolved special traits. For example, they developed ways to hide their nectar. Only certain animals were able to get at the plants hidden nectar. These specific animals might be more likely to visit only flowers of the same species. This was also a benefit for some animals. Animals also evolved special traits to get to the nectar.

What problems could arise if a plant waits for the wind to help it?

We were cornered in a sort of way already. But these butchers up the cavern had been surprised, they were probably scared, and they had no special weapons, only those little hatchets of theirs. And that way lay escape. Their sturdy little forms--ever so much shorter and thicker than the mooncalf herds--were scattered up the slope in a way that was eloquent of indecision. I had the moral advantage of a mad bull in a street. But for all that, there seemed a tremendous crowd of them. Very probably there was. Those Selenites down the cleft had certainly some infernally long spears. It might be they had other surprises for us.... But, confound it! if we charged up the cave we should let them up behind us, and if we didn't those little brutes up the cave would probably get reinforced. Heaven alone knew what tremendous engines of warfare--guns, bombs, terrestrial torpedoes--this unknown world below our feet, this vaster world of which we had only pricked the outer cuticle, might not presently send up to our destruction. It became clear the only thing to do was to charge! It became clearer as the legs of a number of fresh Selenites appeared running down the cavern towards us.
Who was guarding the way to escape?