Corrected entry: Arnie stays in the bathtub all night with out being noticed, which would be impossible because at least SOMEONE had to go to the bathroom in the middle of the night and they would've noticed him.
Corrected entry: How could Arnie get from the top of the tree, to the water tower in such a short period of time?
Correction: You are assuming it's a "short period of time" but you can tell by the daylight changes that a significant amount of time has passed. Gilbert and Becky were simply lost in their conversation and it's perfectly conceivable that Arnie could have wandered away and climbed the water tower.
Corrected entry: In the scene after Arnie has just climbed down the watertower for the first time and Gilbert is standing next to Arnie as they talk to the police. Arnie's hand is up near his face, then in the next shot it is down, then up again in the next.
Correction: Arnie is special. His hand is always near his face the whole movie.
Corrected entry: Gilbert's hair keeps changing it's length and style.
Correction: Gilbert's hair does not change style. It stays thick and straight the whole time. He is getting older so of course his hair will grow.
Corrected entry: When Gilbert is telling about the family and Endora at the beginning of the movie, he says that his father hung himself 17 years earlier. Yet, just seconds earlier he says he has a sister that has just turned 15. How did he father a child born two years after his death? There's no implication that she's a half-sister or adopted. (00:04:50)
Correction: Later in the movie, the truth comes out as Gilbert tells his girlfriend that his father just walked out and never came back.
The dialogue in the scene in question suggests that their father walked out, but later returned to their house to commit suicide. Gilbert specifically says "He was just hangin' there." We also see Arnie sitting next to his father's grave at Ken Carver's funeral, with his date of death reading October 13, 1978. If we assume the movie takes place in 1993, then that actually allows for Ellen to have been conceived or even been born before the father's death, though it would render Gilbert's statement that he died 17 years earlier a character mistake.
Correction: Amy could be close to turning 16, and Gilbert could have rounded up on the years his father's been deceased. Maybe it was 16 years and 7 months, so he just said 17.
Corrected entry: When Becky says, "That was so brave, what your mother did", her mouth movement is out of sync.
Correction: She's not in the shot when speaking.
Correction: What makes you so sure that someone absolutely had to have used the bathroom at night? There were four of us living in the same house and there were plenty of nights when no-one would feel the need. This entry is based on an assumption, nothing more.
Twotall