A basic outline

The Simpsons Movie is a 2007 American animated comedy film based on the animated television series The Simpsons. The film was directed by David Silverman, and stars the regular television cast of Dan Castellaneta, Julie Kavner, Nancy Cartwright, Yeardley Smith, Hank Azaria, Harry Shearer, Tress MacNeille, and Pamela Hayden. It features Albert Brooks as Russ Cargill, the evil head of the Environmental Protection Agency who intends to destroy Springfield after Homer pollutes the lake. As the townspeople exile him and eventually his family abandon him, Homer works to redeem his folly by stopping Cargill's scheme.
Previous attempts to create a film version of The Simpsons failed due to the lack of a script of appropriate length and production crew members. Eventually, producers James L. Brooks, Matt Groening, Al Jean, Mike Scully, and Richard Sakai began development of the film in 2001. A writing team consisting of Scully, Jean, Brooks, Groening, George Meyer, David Mirkin, Mike Reiss, John Swartzwelder, Jon Vitti, Ian Maxtone-Graham, and Matt Selman
was assembled. They conceived numerous plot ideas, with Groening's
being the one developed into a film. The script was re-written over a
hundred times, and this creativity continued after animation had begun
in 2006. This meant hours of finished material was cut, which included cameo roles from Erin Brockovich, Minnie Driver, Isla Fisher, Kelsey Grammer, and Edward Norton. Tom Hanks and Green Day appeared in the final cut as themselves.
Tie-in promotions were made with several companies, including Burger King and 7-Eleven, which transformed selected stores into Kwik-E-Marts. The film premiered in Springfield, Vermont, which had won the right to hold it through a competition organized by Fox. The film was a box office success, as it grossed over $527 million and received generally positive reviews.
The Plot
While performing on Lake Springfield, rock band Green Day are killed when pollution in the lake dissolves their barge, following an audience revolt after frontman Billie Joe Armstrong proposes an environmental discussion. At a memorial service, Grampa has a prophetic vision in which he predicts the impending doom of the town, but only Marge takes it seriously. Lisa and an Irish boy named Colin, with whom she has fallen in love, hold a meeting where they convince the town to clean up the lake.
Meanwhile, Homer adopts a pig from Krusty Burger and names it "Plopper".
Homer stores the pig's feces (and some of his own) in an overflowing
silo which Marge tells him to dispose of safely. However, Homer gets
distracted and instead dumps the silo in the lake, re-polluting it to an
even more severe degree. Moments later, a squirrel jumps into the lake
and becomes severely mutated. Nearby, Flanders and Bart discover the squirrel during a hike, and the EPA captures it. Russ Cargill, head of the EPA, presents five options to President Schwarzenegger to keep the town's pollution contained; he randomly picks option 3, enclosing Springfield in a large glass dome.
When the police discover Homer's silo in the lake, an angry mob of
townspeople approach the Simpsons' home and set the house on fire, but
the family escape through a sinkhole that leads to the outside of the dome, and flee to Alaska.
The trapped citizens damage the dome over time and Cargill, not
wanting news of what he has done to become widespread, plans to destroy
Springfield. In Alaska, the Simpsons see an advertisement, starring Tom Hanks, for a new Grand Canyon
to be located on the site where Springfield is located. Marge and the
kids want to go and save the town, but Homer refuses to help the people
who tried to kill him. The family abandon Homer and leave, but are
captured by the EPA and then put back into the dome. After a visit from a
mysterious Inuit shaman, Homer has an epiphany and believes he must save the town in order to save himself.
As he arrives at Springfield to do so, a helicopter lowers a bomb
suspended by rope through a hole in the dome. Homer climbs to the peak
of the dome and descends the rope, knocking the escaping townspeople and
bomb off. Homer takes the bomb and a motorcycle. After reuniting with
Bart, they cycle up the side of the dome and Bart throws the bomb
through the hole, seconds before detonation. The bomb explodes,
shattering the dome, while with Maggie's help, Bart and Homer deal with
Cargill. The town finally praises Homer, who rides off with Marge on the
motorcycle into the sunrise and kiss each other. The townspeople begin
restoring Springfield back to normal.
(courtesy of Wikipedia)

What did you think of the movie, I loved it and hope they do another and still think the spider pig bit is awesome.