Continuity mistake: When Lisa goes door-to-door with the petition, the door on Milhouse's house has two grooved panels, a tall, 12-panel window, a light fixture above the door, and there's a tree between it and the blue house next door. When Lisa sees Colin and Milhouse again near the end, some of the features of the house have changed - unrelated to the damage Springfield's homes have suffered. The door now has three grooved panels and no mail slot, the window is much shorter, and the light fixture above the door is gone, with no hole in the wall if it had been broken off. The tree between the house and the blue house next door has changed position on the grass as well. (00:09:10)
Continuity mistake: When Nelson punches Milhouse in the stomach, there is a hose hanging below the window attached to a spigot, and the front door has two grooved panels on it, but when the dome approaches and Milhouse swallows his inhaler, the door is flat and smooth, and the hose, its holder and spigot have vanished and been replaced with a bush.
Continuity mistake: When Lisa is going door-to-door with the petition, Milhouse opens his front door and there is no mail slot on the door, but when Nelson punches Milhouse in the stomach there's a mail slot on the door, beside the door knob. (00:09:10)
Continuity mistake: When Bart falls off the roof and grabs hold of the gutter, in the overhead shot the gutter is an L-shape with a 90° angle, but after Homer and Bart high-five each other, the gutter is a straight line that ends at the corner. (00:08:10)
Continuity mistake: When Cargill confronts Homer, he raises his shotgun. In the next shot, his shotgun is suddenly lowered. (01:11:35)
Continuity mistake: When everyone is saying "Lord hear our prayer" at the church, Kirk van Houten is wearing a blue suit, but later when Grandpa is freaking out, Kirk is wearing a red suit. (00:04:05 - 00:05:40)
Continuity mistake: When Homer dumps the silo in the lake, there are the words "Pig Crap" on the front and there is no writing on the back. However, when Lou and Eddie find the silo later in the movie, the "Pig Crap" words are there, but the words saying "Return To Homer Simpson, No Reward" has appeared out of nowhere. (00:23:00 - 00:30:50)
Continuity mistake: When Homer leaves the bar Eski-Moes (in Alaska), he catches hold of a truck, which propels him up the hill in front of his cabin. However, he runs outside a few minutes later and floats away on the heart-shaped iceberg, which has suddenly appeared on a lake that was never there before. The road that the truck was on earlier is gone.
Continuity mistake: The Simpsons enter a motel (Red Rash Inn) to hide, and it's clear from the outside that the building is only one story high. But when Homer flings back the curtains to reveal the buildings and billboards, it appears that the motel room is located on a much higher floor, since the view seems to be level with the building tops.
Continuity mistake: In the scene where they are climbing the rope to escape the dome, the hole seems to be very wide. Yet when Homer is on top of the dome the hole is very small.
Continuity mistake: This is when Homer is about to conquer the 'Ball of Death', on his third attempt. As he is going up, just after Lisa shouts, "Don't slow down, speed up," when Homer has his fingers on the brakes, the Ball of Death suddenly gets a lot bigger.
Continuity mistake: The thickness of the dome changes from when it's dropped on Springfield to when they are escaping.
Continuity mistake: The size of the round window in the church changes size throughout the film.
Factual error: In the scene where the angry mob is attacking the Simpsons in the tree house, Grandpa Simpson is shown aiming a double-barrel shotgun, which he then pumps to ready it for firing. There's no such thing as a double-barrel pump-action shotgun. (00:36:20)
Continuity mistake: During the bike stunt at the end, Homer's hair flows in some shots, but is completely rigid in others. (01:10:00)
Continuity mistake: Marge and Bart discover the wanted poster of them at the gas station. When the clerk enters the scene, his shadow is cast on the wall, cork board and the wanted poster behind him. The clerk never moves, nor does the lighting ever change, but as he says "OK" after Marge asks for diapers, his shadow has vanished.
Continuity mistake: After Marge shouts into the megaphone for the bomb to be thrown, it cuts to Homer and Bart while they're riding sideways on the motorcycle, and the bomb's under Bart's left arm while he's holding onto Homer with his right hand, but in the following shots the bomb's under Bart's right arm while he's holding Homer with his left hand.
Audio problem: When Maggie is trying to point out the sinkhole, Marge says "We'll play later." Her mouth doesn't match what she says.
Factual error: Marge, Bart, Lisa, and Maggie Simpson take the train from Alaska to Seattle, Wash. (The train shown in Alaska, is the exact same one that arrives in Seattle). This is not possible as there is no train, (passenger or freight), that links Alaska to the southern 48 states, including Seattle, Wash. Homer Simpson does not take the train to the southern 48 states.
Continuity mistake: In the exterior shot of the Simpson house, before showing Homer and Marge watching the news about the silo being found in the lake, we see the side window (facing the Flanders' house, from which they escape later) is a horizontal sliding window. However, from inside the bedroom and also when they are escaping, that same window has changed to a vertical sliding window. The same thing happens with the other window on the opposite side of their chimney.
Answer: Homer has been known not to make the smartest decisions, and the decisions he does make, he makes without fully thinking them through. Clearly he wanted to get some donuts as quickly as possible without thinking of any other ways, so he decided to ditch the silo in the lake as it would be the fastest way of getting it off his back, even if it's not the smartest. Also, putting that aside, he likely wanted his own pick of the donuts rather than have Lenny guess what he wanted.
Casual Person