Blooper

(at around 12 mins) After the automobile accident, Sam climbs out of bed in his bare feet. Sam walks out of the bedroom and the camera zooms in on Sam's bare feet as he continues down the hall. We see another shot of Sam's bare feet as he ambles down the stairs to the kitchen. Sam's dad, who is on the front porch, sees Sam through the kitchen door and calls out to him. As Sam instantly runs to meet his dad, we clearly hear the sound of Sam's bare feet slapping on the hardwood floor as he races across it. But as he barrels through the kitchen door onto the porch, Sam suddenly and miraculously has his boots on.

(at around 7 mins) When the old man is smoking his cigarette grows from one shot to the next, from almost gone to half smoked.

(at around 17 mins) When Lance Henriksen's character is introducing his hobby of comic collecting, he says that the Marvel Tales comic he is holding is a first print from 1964 but on the back cover there is an advertisement for Battletoads (1991) the videogame meaning the comic was actually from around 1991.

(at around 1h 27 mins) When the kid and his dad get ready to leave, the truck starts before they get in it.

This is not a goof, but a classic J-cut transition where the audio portion of the later scene (David and Sam leaving in the truck) starts playing before its picture.