Continuity mistake: When Homer is eating a krusty burger you can see crumbs on his face, but in the next shot of him talking the crumbs have vanished.
Other mistake: At the end of Marge's video message to Homer, Marge explains she taped the message over their wedding video. The video then shows the remainder of Homer and Marge's wedding. This is inconsistent with The Simpsons' Season 3 episode "I Married Marge" and Season 8's "A Milhouse Divided," which show Homer and Marge marrying at a chapel on the state line and later Homer and Marge alone eating cake together in a parking lot.
Continuity mistake: When Homer tries to convince Bart to come with him on the motorbike, he first holds the bomb in his right hand, but then it's in his left one in a different angle.
Continuity mistake: When the spaceship is landing, there are no craters near, but when Scratchy gets out, there are some craters there. (00:00:31)
Continuity mistake: When Mayor Quimby asks Cletus to demonstrate the anti-pollution barriers around the lake are idiot-proof, his entourage is spread apart, but the next shot of Quimby shows his entourage bunched closer together behind him.
Continuity mistake: When Homer and Bart are trying to outrun the crack in the dome, they are falling towards the damaged "P" in the Springfield sign. From their view, the top of the "P" is level with the letters "S" and "R" but when they use the bent leg of the "P" as a ramp to relaunch themselves at the dome, the top of the "P" is scrunched down almost halfway down from the other letters.
Continuity mistake: When the dome is lowered it is done so by 100s of helicopters that release the dome as Homer runs outside. The camera zooms out to show the whole dome and the helicopters have disappeared instantly. (00:26:20)
Other mistake: When Marge is watching the recording of Grandpa on the cell phone, the camera changes positions suddenly after he says "Trapped forever." How could an old-fashioned flip phone pause like that? Also, in the 2nd view, it shows a floor-to-subject camera angle - the only way that could be possible is if there is a hole in the floor and someone's recording through it. (00:10:46)
Answer: The family doesn't treat him very well, particularly Homer. He may have wanted some revenge on them. Grampa is also a little senile.
Phaneron ★