Continuity mistake: Right before the Demolition Robot starts tearing through the house, Spooner is talking to the cat, and in the close up shots of the cat it is sitting down, but in the shots of Spooner with the cat, it is standing up.
Continuity mistake: Scenes showing the elevator descending from outside the elevator at the USR building are MUCH faster than the scenes showing its speed descending from inside. They don't even come close to matching.
Revealing mistake: In the climax of the movie when Spooner and Calvin are fighting off the robots, there is a shot of Spooner standing on one of the catwalks shooting the robots as the camera spins around vertically. At the end of this shot if you look closely you can see Spooner's neck stretch out as if he was getting choked well before the robot actually grabs him.
Continuity mistake: Close to the beginning of the film when we see Del and his boss in the bar drinking together, just before Del leaves, you see his boss put his hand up to his head, in one shot, you can see he actually has a closed fist to his head, then in the following shot, his hand is open and on top of his head. (00:34:15)
Continuity mistake: At the start of the film when Del is in the USR building and is looking over Dr Lanning's body, if you notice the shoe changes position from being not far from the body to some distance, also, it changes direction from the first time we see it, we are looking at the heel of the boot or the front, then it is completely side on in the next shot. (00:10:55)
Plot hole: Sonny hides among the 1000 robots in the big store room. They are all placed in very straight rows. Sonny would not be able to take over another robot's place in the grid (when he starts running we see a large robot-sized gap) without getting another robot to move. And while Will Smith is running around the rows, he would have noticed if the others moved to make room.
Continuity mistake: The robots pouncing on Spooner's car. When Spooner shoots the robot on his left, a robot at the right smashes the front right side of the windshield and grabs the gun. The scene shifts outside where the robot with the gun is falling off. The windshield on the right is no longer damaged over there. A little later during the same scenes continuation, another robot jumps and breaks the entire windshield.
Continuity mistake: After the accident where the car topples over, the pillar is damaged and pushes the car behind because of the impact force. Subsequent scenes show the pillar repaired and the car touching the pillar.
Continuity mistake: The bleeding wound Spooner sustains on the right side of his head during his escape from Dr. Lanning's home as it's being demolished is completely healed without a trace later in the film, although others on his face he sustained during the robots' attack on his car remain visible.