During the first shootout, the same headlight of the enemy's vehicle gets shot out three different times.
The chest pocket on Chad's pink shirt changes sides (the shot has obviously been horizontally flipped).
When Chad and Danielle are chasing Griffith between the containers, Griffith's shadow is cast back and Chad and Danielle's shadow is cast forward.
When Chad is talking to Alex about going after the gang, right after they meet for the first time, Danielle is standing behind Alex in an angle shot from their right side. Danielle is almost touching Alex with her folded arms. The next instant the camera is shooting over Chad's shoulder and Danielle is several feet behind Alex with her same pose as in the previous angle. She would not have had time to move that far in a split second.
During the first shootout, Alex fires at least 60 rounds from two 10-round Berettas without reloading.
One of the oil barrels being flung around by Moon is made from foam rubber. It creases as he runs toward the camera with it.
When Chad hangs from a warehouse ledge, the street below is a blue screen effect, visible to the naked eye.
During the "factory" shootout, the bad guy in the blue shirt has a large fake blood spot on his right chest while he is still actively firing at Chad.
When Chad comes back to the hideout to find Alex drunk, Alex is transparent when the twins are in the same shot.
When Chad and Danielle are on the boat after their swim in the harbor, Chad's clothes are perfectly dry while hers are hung on a line down below to dry out. However, her hair has the look as if it has been blown dry. It's doubtful Alex would have carried a blow dryer on his boat.
Right after Chad kicks open the side door of his brother's parlor to escape the goons, the set is clearly visible outside of the door.
When Frank Avery is driving the red sports car back to the house to rescue the family, the shadow of the camera attached to the bonnet/hood is visible on the roadside to the left.
Frank and Chad take a plane to Hong Kong that says Philippines Airlines but Hong Kong is in China over 800 miles away.
As a baby, neither those who took him into the orphanage nor Alex himself would have known his name.