Continuity mistake: As Cobb is finishing describing how powerful a dream is, his right arm hangs down out of sight as his left thumb touches his forehead, then drops to rest on the table. A wine glass stands to his left. When the viewing angle reverses, his left arm is instantly hanging so that the hand is in his lap, and his right hand is bringing the wine glass to his mouth, yet the conversation is real-time continuous. (00:03:10)johnrosa
Continuity mistake: In the scene where Ariadne finds out that the only way Cobb can dream is by being hooked up to the machine. When she first walks in and sees him sleeping on the chair she has a purse over her left arm. But in the next shot, she has no purse on either shoulder and there's no shot showing her putting the purse down. (00:54:20)
Continuity mistake: In the scene on the airplane when they are setting up to go under, Yusuf takes a sip from a wine glass and goes to set it down. Then in the shot immediately following he no longer has a wine glass in his hand. Instead he is buckling his seat belt. (01:03:50)
Continuity mistake: When the train comes barreling down the street in the level 1 dream (on the plane) in the rain, the length changes. In an overhead shot we can see what appears to be three cars (including engine). It is moving quite quickly and should pass them in no time, but Cobb has to back around the train and catch up. It appears as he is backing around that more than three train cars have passed. (01:06:05)hal.hockersmith
Deliberate mistake: The exact same filmed footage of sleeping Arthur is shown in two different scenes inside the van. This repeated slow-motion scene shows his left hand rising and two spherical droplets of water drift towards his right eye. It can be first seen when the van is being chased out of an alley and makes a right turn onto a street. Then it can be seen again soon after the motorcycle rider smashes into the windscreen. Watch for it when the van passes through open gates and makes a right turn. (01:29:30 - 01:38:55)
Revealing mistake: When Ariadne is pulling the two huge mirrors close together underneath the bridge with Cobb, watch her when she is closing the second mirror. She steps over something even though there is nothing present for her to step over. There must have been a green screen frame there for her to step over.
Continuity mistake: At the beginning of the movie, when Cobb and Arthur are on the top of the building about to get into a helicopter to leave, they find Saito in their helicopter. During the dialogue between Saito and Cobb, the window of the helicopter behind Saito is wet and being rained on. But when the camera cuts to Cobb outside the helicopter, it is not raining at all. This happens multiple times in the scene. As the helicopter flies away at the end of the scene, there is no rain.
Deliberate mistake: During the mob scene outside Saito's love nest, the same black Saab is seen getting firebombed twice. It was shot from two different angles, with the two shots played about a minute apart to give the impression of two cars getting bombed. Also, in the first angle it is clear the car has no engine.