Amount of blood on Trey's jeans, when he enters his home to get the gun after Rick is shot, then the jeans have less amount of blood when he gets out of Doughboy's car and then back to the same amount again when he comes back home.
In the alley scene where Ricky is shot and killed, he is shown running with his long sleeves rolled up before he gets shot. After he gets shot and Tre reaches him, Ricky's sleeves are pulled all the way down.
When Ferris fires his gun during the Crenshaw Blvd scene, the girl in the pink coat he is with reacts in the shot focused on the red car, when he had already been firing several rounds previous to this shot.
When the "boyz" are driving late at night looking for the guys who shot Ricky, Dooky is sitting in the front seat with a pacifier in his mouth. He turns around towards the back seat and says, "Let's get something to eat" - and when the camera angle changes, the pacifier has disappeared.
When Tre's Mom is dropping him off at his dad's house, the street and his dad's driveway are sunny, with no shade. After his dad tells the neighborhood kids he'll give them $5.00 for raking leaves on his lawn, the street and driveway are completely in shade.
When Ricky is a child at the beginning, the gang member asks for the football so he can give it back to Ricky. Although he had the football a second earlier, he only changes his mind after Ricky turns back to face him, making him feel guilty.
When Trey first arrives at his father's house the lawn is full of leaves, like it would be during the Autumn season. But all the trees and bushes in the neighborhood are very green and none of the other lawns have any leaves on them at all.