Hancock talks to Mary while eating a banana, which changes from eaten to uneaten, and back again.
Ray picks up a tri-colored towel, then opens a jar with a green and gold towel.
When Hancock throws Ray's car into the other cars and stops the train, Ray's windshield cracks. When Hancock drags the car into the driveway a few minutes later, the windshield is intact.
When Hancock first arrives at Ray's house, the amount of spaghetti and meatballs in the bowl changes between shots.
When Ray is waiting in traffic on the train tracks, he talks on a cell phone at his left ear, then ends the conversation. In a later long shot, the phone is still at his left ear.
When Hancock stopped the train, the impact speed should've seriously injured or killed the locomotive engineer.
During the shootout outside the bank, the bullet holes in the police cruisers are dented in, as if they were fired from the side of the car the officers are hiding on. If the bullets were coming from the other side, the holes should be bent outward.
When Hancock throws the whale back into the sea, the water splash appears before the whale actually hits the water.
Ray chops of Red's hand with an axe yet there is no arterial bleeding as expected.
When Hancock is using the car to rescue the officer it wouldn't have provided much protection due to the thin steel bodyshell.
When the people are running away from the tornadoes, suddenly a strange character runs from the left to the right of the screen. The character is twice as tall as everyone else, and looks like a robot or an alien. It may be a street performer, on stilts and in costume.
After Ray meets Hancock for the first time, when the camera follows Ray and Mary's dog across the bedroom, what appears to be a crew member pushing the dog from behind the dresser is actually the shadow of the dog's tail on the wall. However, the dog is clearly watching something or someone behind the bed for a signal.
When Hancock throws Michel into the air, then catches him, the car in the background, which is hit by the refrigerator later, is already damaged. Only the windows are broken, and that could've been caused by flying pieces of asphalt or the concussion of Hancock's landing.
When Ray is on the train tracks, his seat belt is stuck. After Hancock flips the car, Ray is laying on the inside of the roof, with the seat belt undone. A seat belt is harder to unlatch when it has tension on it, as would be the case when hanging upside-down. Ray could have a car safety hammer, a small tool that can cut a seat belt.
When Hancock is shot inside the convenience store, he is shot one time in the abdomen. The TV News report says he had been shot multiple times... As the camera pans down from Hancock's face, there are clearly two bullet wounds on his left and right abdomen before he moves his hands over them. (1:09:51)
When Hancock and Ray are talking through the glass in prison, the cutout Hancock is about to make in the glass is clearly visible, especially running across Ray's right cheek.
When Hancock picks up the police cruiser to protect the downed female officer, the car has no transmission or drive shaft.
When Ray is about to be hit by the train, long shots show his car on the tracks. Shots from inside the car show that the car isn't on the tracks.
Hancock first appears, in a drunken stupor, on a bus bench that faces away from the street, instead of toward the street, where passengers would normally approach and board buses.
The size of the rolling pin Hancock uses to bash Mary over the head changes length between the counter top and striking range. In fact, the rolling pin seems to grow when Hancock holds it.
Mary slams the refrigerator (and Hancock) through the window onto an outside parked cars when Hancock attempts to kiss her. The next morning she takes out some eggs from the fridge. All these eggs should have been crushed after throwing out the fridge with that kind of force.
Before heading to the bank, Hancock shaves his face by using his fingernails. Since hair and fingernails are the same substance (keratin), he shouldn't have been able to "cut" one with the other.
When Hancock uses the cop car as a shield against guns, he holds it with the roof of the car away from him. Cop cars have bulletproof sides and doors, but not bulletproof roofs or undercarriages. Therefore the bullets would've actually gone through the car the way Hancock was using it.
In the opening scenes, Hancock drinks Seagram's 7 whiskey from a 1.75 liter bottle. The bottles shown are obviously plastic, but when they roll on the ground, or are shattered, they sound like glass.
Monitors are reflected in Hancock's glasses throughout the movie.
In the opening sequence, Hancock stops a band of criminals. The reporter on TV is heard stating that they are on the 105 freeway. However, when he picks up the SUV, downtown LA is shown. The 105 freeway goes nowhere near Downtown Los Angeles.
Mary intends to keep her special powers and immortality a secret so that she can be in a "normal" relationship with Ray. That kind of a secret is bound to be uncovered as years pass and she does not age.
In the YouTube video of Walter the whale, Ray calls Walter a gray whale. Walter is clearly a humpback whale.