Continuity mistake: When Ariadne wakes in the Snow Fortress and the floor goes from under her, we can see her gloves fall in to the crack but in a different camera shot of her we can see the gloves are now back near her head again. (02:12:20)
Continuity mistake: When they escape from the building in the first dream, the right-hand mirror of the van is broken by the narrow gate. In the following shot when they are driving, the other mirror is broken and the right mirror is suddenly undamaged.
Continuity mistake: In the hotel scene when Ariadne and Arthur are sitting watching Mr Charles walk in to talk to Fischer, we can see she has earrings, but later when Ariadne asks "wait, whose subconscious are we going into?" we can briefly see she has no earrings.
Continuity mistake: When Cobb and Arthur are leaving their hotel room to get on a helicopter on the roof, we can see it's quite dark outside. But in the shot of them on the roof, it's much brighter.
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.
Continuity mistake: Third dream level, there are six henchmen being pulled by the Hummer snowmobile, and the back right gets shot off (or taken out). A scene a few minutes later, the missing henchman is back, then a few minutes later he is gone again.
Continuity mistake: As the van is in free-fall from the bridge to the water, Arthur's headphones disappear and then reappear between various shots.
Continuity mistake: When Arthur is fighting the projection in the hallway and begins to strangle him using the projections arm, we see his arm is covering his mouth.However in the next shot his arm is around his neck and his mouth is uncovered. (01:48:55)
Continuity mistake: In the second scene, when Cobb is taken to Saito (Old Man), Cobb's totem is kept on the table with the longer end down. But as the PoV changes to Saito's, the totem keeps changing position with the shorter end down. This happens at least four times. (00:01:45)
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 second layer of the dream, when Ariadne and Arthur are sitting together, Ariadne's hair changes between shots. At some times, her updo is tied on top of her head, and sometimes, it is a bun at the back. It looks as if the hair is completely opened and tied again in a different way between shots. It must be because of the shots being recorded at different times.
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)
Continuity mistake: During the vehicle chase in the first dream, the taxi's driver's side windows are shot out. In the next shot, while it is backing up and hitting another car, the windows are intact. And in the next shot, the windows are broken again. (01:04:30 - 01:06:00)
Continuity mistake: During the shifting gravity scene in the hotel room, Arthur rolls off the bed, catches the gun, and shoots the projection. As they slide towards the door, Arthur is curled up and facing away from the projection. But in the next shot, when we see them close up, Arthur is facing toward the projection and is no longer curled up.
Continuity mistake: When Ariadne is learning how to make/change terrain, she shifts gravity and makes buildings touch the top of other buildings. However, if you look in the windows of the black hatchback or any other car, you can see sky and clouds visible.
Continuity mistake: In the beginning, after Nash dumps Cobb into the tub, Saito grabs Nash from behind, hits him, and then turns around and points his gun at Arthur. Nash is dry. But, in the next shot, Cobb jumps out of the tub and wrestles Saito to the ground. Before Cobb grabs Saito, it is shown that Nash is now soaked.
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)
Continuity mistake: Just before the shifting gravity, Arthur walks out of the room and begins walking down the hallway. As we see him from behind, the elevator door opens and a projection is revealed. But, when the elevator doors are opening, Arthur slows down and just before we see him from the front view shot, his bead begins to tilt down. Then in the front view shot, he slows and tilts his head down again to avoid the projections contact.
Continuity mistake: After the 1st-level shootout in the rainy streets, the two cars arrive at a warehouse. As they drive in, we see the wet tracks their tires left in previous takes of the same entry. (01:07:20)
Continuity mistake: In the climax scene when Cobb embraces his children, in the first frame he lifts up Philipa, but a moment later in the next frame, we observe that its James now in his arms while Philippa clings on to his leg. (02:17:05)
Answer: The answer above is solid and I agree, but there's another plausible way of looking at it. It is implied at the end that Cobb could still be dreaming (we never see if the top stops spinning). If that's the case, then he would likely dream his children to be exactly how he remembers them.
jshy7979