The film was rated PG-13 by the MPAA (Motion Picture Association of America) for "irreverent humor throughout".
The film's "color and shading" was brighter than the one used on the show, since the film is made in a 16:9 aspect.
Dr. Nick Riviera is presumably killed by a giant piece of the dome's glass, yet in the Season 20 episode "Lost Verizon" he is seen alive. It might be possible that he was just seriously injured by the large piece of glass, and could have just passed out.
There were people outside the dome guarding it, so they would probably get in trouble with them if they dug out anyway and they figured it was better not to do it.
Another way one could interpret Grampa's message is "Twisted tale, A thousand eyes, trapped forever" (Eyes referring the Springfieldians's), or the "ayes" the Springfieldians said in favor of a new scissor lift at the town meeting.
Marge was originally going to be the one to give the warning. But the writers scrapped that because they didn't think it was right for a man to roll up his wife in a carpet.
It was also going to be Eleanor Abernathy, but that idea was removed, too.
The family was originally going to go to Homer, Alaska rather than Nome, Alaska, because Homer felt he could fit in with other "Homers".
In the torch mob part, a "Lord Of The Rings" orc with an axe can be seen.
When Homer's phone is ringing, the Nokia tune plays over it when he got a call from Lenny where he tells that the donut shop is closing down and selling free doughnuts.
It is insinuated that the reason the Nokia tune is played is because most "No mobiles allowed" adverts use this ringtone. It is also the best known ringtone in the world.
The film was given a PG in the USA (PG in the UK) classification due to brief nudity. The only nudity is when Bart's "penis" is shown on-screen during the skateboard scene.
In the angry mob scene, Ralph, Sideshow Bob, and Mr. Burns were not seen, (although Smithers was in the mob, and Sarah and Chief Wiggum wouldn't leave Ralph unsupervised). Although, on a "The Simpsons Movie" poster, Homer is being chased by the angry mob, and Mr. Burns and Sideshow Bob were seen in it. This may imply that they were in the mob in the actual movie.
In the angry mob scene, some of the characters were duplicated (Princess Kashmir, Martha Prince and Marcus Le Marquez for example), most likely because there weren't enough characters to look like the entirety of Springfield.
Homer said that the angry mob chased them at 4:00 in the afternoon, but Marge said it was 7:00 pm. However, the grandfather clock that got swallowed up by the sinkhole said 4:43. It could be implied that Homer was right.
Some of the people in the mob were carrying other weapons instead of torches. The Sea Captain is brandishing a meat hook, the Orc is using an axe, and Jeffery Albertson is holding a lightsaber (it might not be a prop, since the mob is intending to literally kill Homer, it might be real). In the poster, Chief Wiggum is using his baton, Sideshow Bob is using his carving knife, Luigi is using a ladle, The Rich Texan has his guns, and Groundskeeper Willie has his rake (coincidentally, and to make things more humoring, Willie's rake is right in front of Sideshow Bob).
In the big mob shot, Richard can be seen holding his torch with both of his hands.
When the sinkhole destroys the house, a chiming grandfather clock can be seen, but when the sinkhole stops expanding, and everything collapses, a cuckoo bird pops up and "cuckoos". Cuckoo birds come out of cuckoo clocks, not grandfather clocks.
In the big mob shot, the pastor, Robert H. Schuller can be seen with his bible. He previously appeared in "Natural Born Kissers", where he was much younger.
In the mob scene, The Orc can be seen again in the big shot where the townspeople are carrying the car to the backyard.
In the big mob shot, the Springfield Elementary children are wearing their regular clothing, but when they shoot their arrows, they are wearing light blue sweaters. In a movie trailer, the sweaters are labeled with text saying "Springfield Archery". In the movie, the text is gone in one shot, but reappears in the next shot when Nelson is about to shoot his red arrow.
Homer says that they are staying in Alaska, and that they are never going back to America again. However, Alaska is a US state, and so part of America. However, Homer might not have known this.
When Homer's "pig crap" silo is found in the poisoned lake, and when Kent Brockman tells the townspeople to "get him", the entire town formed a vigilante angry mob in four seconds, when normally, it would take hours for an entire town to get together.
While Kent Brockman tells the townspeople to get him, Officer Eddie writes on his notepad, "Illegal dumping pig crap, Homer Simpson". The first letters in Homer's first and last name is lowercase and not capitalized. Not to mention the text on Eddie's notepad is written over his hand and uniform.
In an unreleased deleted scene, in place of Homer saying "Marge, look, those idiots don't even know where we live!!" Sideshow Bob was going to be in the back of the mob shot, further proving that he was in the mob.
When the townspeople approach to the Simpsons house chanting "We want Homer!", the same townspeople are shown outside the window, with more characters added. However, Birch Barlow is replaced with Fat Tony, and Krusty, Luigi, Otto, Smithers, Bumblebee Man, and Chief Wiggum are missing. This must be because they were the ones that rammed the door down, along with Manjula, but she was shown outside the window. Chief Wiggum was replaced by Officer Eddie.
When the angry mob claws Homer's head, Groundskeeper Willie scrapes Homer's head with his rake.
In the angry mob scene, many people confused Dexter Colt for Rex Banner, and Rex Banner has not appeared in the movie, meaning that Rex Banner could be deceased.
When Bart is reunited with Santa's Little Helper, Bart asks the dog how he had fared and the dog barks in reply. On the DVD at this point, if "English for the Hard of Hearing" subtitles are on, the barks are subtitled as English words.
The scene with Homer on the wrecking ball makes a cameo in the GLaD to See You level in LEGO Dimensions.
Due to the movie format, some scenes were in the film that would not have been included in the TV series due to censorship reasons:
During Bart's streaking scene, there was a brief shot of his penis being visible.
Homer when jumping into the sinkhole to escape from the congregated mob proceeds to briefly do double middle fingers at them (though because the characters have four fingers, it isn't particularly obvious) before prematurely stopping (and thus forcing him to dig down to evade them).
Marge briefly witnesses two male cops arrive near a hotel (narrowly avoiding being caught by the two cops), who then proceed to make out before ducking into a bathroom.
Disney: Homer and Marge's love scene parodies many Disney films, with Disney-style animals helping them undress. Also, Bart, while wearing a black bra on his head like Disney-style ears, impersonates Mickey Mouse on the train, calling himself "the mascot of an evil corporation".
Grand Theft Auto: Homer plays Grand Theft Walrus, an allusion to the video game series.
Happy Feet: In the above game, his character shoots a tap-dancing penguin in reference to the film.
Harry Potter: Homer renames Spider-Pig Harry "Plopper" and dresses him in glasses and a lightning scar, a reference to the Harry Potter character.
An Inconvenient Truth: The name of Lisa's lecture, An Irritating Truth, is a play on Al Gore's documentary.
Full Metal Jacket: The bomb disposal robot was based on Vincent D'Onofrio's character Leonard "Pyle" Lawrence, who commits suicide in a similar way.
Star Wars Episode VI: Return of the Jedi: At the end of the film, the crowd's celebration is similar to the conclusion of the final Star Wars film, with Carl performing exactly the same hand gestures as Lando Calrissian.
Independence Day: The scene where the EPA Dome is delivered to Springfield (notably the immense shadow covering Springfield and the People's reactions) resembles the Alien Destroyers positioning themselves over Washington DC, New York City, and Los Angeles scenes in the movie.
Nome, Alaska: In Alaska, when Marge is knitting, she knits the words, "Nome, Sweet Nome", a reference to the city Nome, Alaska. This is also a nod to the Pixar short "Knick Knack", in which the same phrase appears on snowman Nick's snowglobe.
Between a rock and a hard place: When Homer gets repeatedly slammed into a building called A Hard Place and a rock by the wrecking ball, it is a reference to the saying, meaning to solve a dilemma.
During the cleanup of Lake Springfield, when Fat Tony is stopped from dumping something into the river due to the cleanup, Fat Tony simply comments that he'll dump his "yard trimmings" into a car compacter, with his fellow gang members carrying a rug containing a presumably dead body (which Lou noticed and tried to warn Wiggum, but was ignored). Yard trimmings is gang language for disposing of a dead body.
Arnold Schwarzenegger: Arnold Schwarzenegger is the president.
Moe's Tavern says "Moe's Bar".
Willie is seen with brown hair instead of red throughout the movie until the end when it is seen as its usual red.
When Homer's motorcycle lands on to the ground he is on a lawn, but in the next shot they are on a cliff instead of a lawn.
When Bart tumbles down the roof, his shirt color is light pink instead of orange.
During the town meeting held by Lisa the places where people are sitting constantly change.
When Bart was clapping to cause an avalanche in Alaska, the number of logs Homer is holding constantly changes.
Colin's tie changes between shots during his brief encounter with Lisa after the family exits the dome.
Russ' tie change from purple to blue between shots, after the family flees the dome. The tie's color only changes because of the light, it changes mildly at best.
When Ned is seen cleaning his son's beds, the pictures above them are sheep. But when he talks to Bart, the picture shown is of Ned and his boys.
When Russ Cargill is talking to the town on a monitor on the dome, you see where the dome cuts off the town and that Evergreen Terrace is a dead end after the Simpsons home. In the series, the street continues and the house next to the Simpsons once belonged to Ruth Powers and her daughter Laura.
When Jeffery Albertson shows Marge his recording of Grampa's vision, the time he paused between each sentence is drastically altered.
When Homer is collecting logs and Bart is causing avalanches with his clapping, the sky is only a light sunset. But when Homer goes inside, the sky is dark with stars.
Marge, Bart, Lisa, and Maggie Simpson ride a passenger train from Alaska to Seattle. The train shown in Seattle is the same one that is shown in Alaska. This is impossible because there is no rail link (passenger or freight) between Alaska and the other 48 states. Homer does not ride the train between Alaska and Seattle.
In the mob scene right before the camera goes through the characters, Astrid Weller has froze and does not move. Also, some characters (such as Kirk Van Houten, and Rabbi Hyman Krustofsky) blink once in one frame, and the orc with the axe is missing. These goofs are probably due to a computer error, although these errors were not made in the trailer.
During the aftermath of the dome being lowered, when the Springfieldians look up at Russ Cargill's giant screen, Handsome Pete is holding his concertina. In the next shot, his concertina is gone.
In the mob scene, Sarah Wiggum's sleeve roll up turns yellow instead of white in one frame.
In the mob scene, The Sea Captain, Groundskeeper Willie, Jacques, Superintendent Chalmers, Chief Wiggum, Officer Eddie, Mr. Largo, Fat Tony, Tab Spangler, and Raphael are the only ones seen chanting "Kill, kill, kill!" unlike the rest of the crowd, who are clamoring indistinctly. Although in the trailer, they are clamoring with the rest of the crowd, and their faces have changed, along with Dexter Colt, Judge Roy Snyder, Gavin's Mom, Martin Prince, and Chester J. Lampwick.
Arnie Pye is barely seen in the mob scene because his size has been shortened for some reason. He is almost as short as Kearney.
When the mob approaches The Simpsons' house, Disco Stu's torch switches hands. The same mistake is made with Groundskeeper Willie, Jasper Beardly, Professor Frink, Miss Hoover, Manjula Nahasapeemapetilon, and Kirk Van Houten. And Comic Book Guy's lightsaber switches hands as well. Not to mention that some of the members' torches are missing, along with the Sea Captain's hook.
In the angry mob scene, Sam, Moe, Lenny, Carl, and Charlie are not visible until the mob turns around.
During the aftermath of the dome being lowered, Nelson is in the crowd right behind Sideshow Mel, then when they look up at Russ Cargill's giant TV screen, he is right next to Astrid Weller. Then in the next shot, Astrid Weller is replaced by Lindsey Naegle.
After Marge, Bart, Lisa and Maggie fell asleep by the gas. Bart is missing his nose as Lisa was about to kick his leg.
When the townspeople see the Simpsons going down the sinkhole, Carl, Cora, and Garth Motherloving are duplicated.
In all of the mob shots, the places where the townspeople stand constantly change, their weapons and torches switch hands, disappear, and reappear.
The rake Groundskeeper Willie claws Homer's head with is shorter in the next shot that came afterwards, and ten of the teeth on the rake disappear, leaving only three.
Levels - Replacement of the first president meeting in scene 10
Springfield News - After Marge finds out Maggie got out in scene 11.
DMV - Before people try to destroy the dome in scene 16.
Sausage Truck - Before Homer climbs the hill and finds out his family is captured in scene 19.
Slightly Alternate Ending - the same as the last part in scene 23 where a new house for the Simpsons is built. The only difference is Plopper, the "thousand-eyed" squirrel and Santa's Little Helper are painting a dog house.
Homer misunderstands Marge - Homer is brushing Plopper's hair and Marge asks him what Homer's doing with Plopper's crap with various euphemisms, although Homer doesn't understand until she whispers into his ear, where it then cuts to the scene where Homer shows her the silo. Al Jean tweeted the screenplay for the scene as part of the film's 10th anniversary.
Cut lead-in to the pig crap silo introduction, part 1.
Cut lead-in to the pig crap silo introduction, part 2.