One car explosion is shown twice. First, the car explodes in a fireball, filling the frame. Minutes later, the same car explodes in the same fireball, but as part of a bigger shot from further away, in the bottom half of the frame.
Cobb and Ariadne are walking along the bridge and Cobb is explaining the importance of not building entire areas from memories. In the single shot of Cobb it's clear he's swinging both arms while walking. In the 2-shot he has his left hand in his pocket.
The first time the cab is hit, the front grille with the Hyundai logo is smashed in, and disappears. The grille reappears in the next scene, and the car has less damage than before. In the warehouse scene, the grille disappears again.
When the white van emerges from the warehouse, the passenger side mirror strikes the warehouse door. In the next shot of van's exterior, the passenger side mirror is fully extended and instead the driver's side mirror is flipped back. In subsequent shots, the correct mirror is flipped back.
When Arthur is tying up the team in the hotel scene, Eames' arms are tightly bound to his sides. When Arthur is pushing them down the corridors, Eames' arms float freely. Then, in the shot looking down into the elevator, his arms are once again bound tightly.
Arthur fights a projection in the rotating hallway, and they slide into a room. When everything finally comes to a stop, and he shoots the projection, he curls up to his left. When he gets up, he straightens up from his right.
In the warehouse, while Cobb and the team are talk about the idea of inception, Cobb rolls up his sleeve, then starts rolling up the next sleeve. The camera cuts away, then moves back to Cobb, who is rolling up his sleeves again.
After the van falls into the water, Fischer saves Peter Browning (actually Eames) from drowning in the van. Saito's eyes are wide open. Back inside the submerged van, when Arthur and Ariadne are breathing from the oxygen tank, Saito's eyes are closed.
When the rain-soaked cars enter the warehouse, the floor already has wet tire tracks, evidently from a previous take. Once they stop and the people exit, the floor behind the cab and back towards the door is dry.
In the first dream sharing of Ariadne and Cobb, when Cobb wants her to think about how they ended up there, in the close shot Cobb hasn't crossed his arms. Then suddenly in the long shot he has crossed his arms, and in the next close shot they are un-crossed again.
When the helicopter sets down at the airport, there is lots of water on the ground, and the rotor makes large ripples on it. When Saito calls to Cobb asking him if he would like to go home, the water is gone. It reappears when the helicopter takes off again.
When Ariadne goes into Cobb's dreams, she is in the elevator and passes the train in limbo. Behind the train is a body of water and the a hilly landscape with houses, not the abandoned cityscape of Cobb's perception of limbo.
When Ariadne is showing Cobb her dream level layouts a Nikon camera is visible besides Cobb at the desk he sits down at. The camera angle looks at Ariadne, then returns back to looking at Cobb and the camera on the desk is gone.
Saito's helicopter takes off from a rooftop in Tokyo, with the distinctive red and white Tokyo Tower in the background of several shots. But it lands moments later at the ultra-modern Farnborough Airport in England, more than 5,900 miles away.
After the initial dream sequence, on board the Bullet Train, Cobb states that he's "...getting off at Kyoto." In the next establishing shot, we can clearly see that the city Cobb is in is Tokyo (judging by the presence of Tokyo Tower). Kyoto is over 200 miles away from Tokyo.
Cobb tells Ariadne to draw a maze in two minutes that takes more than one minute to solve. She eventually draws a circular maze. The circular maze seems to be unsolvable by Cobb. However, it is solvable, and it would probably take most children less than a minute to solve.
The characters dream during a 10-hour flight from Sydney to Los Angeles on a Boeing 747. In real life, a 747 flight from Sydney to LAX takes at least 13.5 hours. The characters need 10 hours to complete the inception, regardless of how long the flight takes.
When the bus on the bridge hits the guardrail, it flies horizontally for some time, but the passengers immediately become weightless. That is correct; weightlessness is caused by acceleration, not speed. Falling is a vertical acceleration, and gravity will immediately cause the bus to fall as soon as it is no longer supported by the bridge.
When the train engine hits the cars, it is clearly affected by the mass of the cars it pushes, and its bouncing movements suggest some form of suspension (or rubber wheels). A real freight engine weighs more than 100 metric tons, far more than the cars it hits. It would not give way or bounce when hitting cars. However, the train appears in a dream, so the laws of physics may not apply. Further indication of this is that the train's wheels are shown running on non-existing rails in/under the asphalt. In real life it would not continue in a straight line.
When Ariadne and Cobb are at the café, a man in a yellow jacket passes behind Cobb. The camera switches back and forth between Cobb and Ariadne several times. When it switches back to Cobb, the man in the yellow jacket passes once again. The person in the jacket is a projection and based on what the movie explains, projections behave a lot like extras. This means the same projection may reappear like that.
On the flight from Sydney to LAX, a flight attendant gives Cobb a white I-94 immigration form, for people coming to the US on a visa. US citizens only need to fill out a smaller blue customs declaration form. Cobb clearly declines the white form. The flight attendant also offers Fischer an I-94. He takes it and sets it down. Fischer is an Australian citizen; his passport is visible when he sits down and Cobb looks at it. Australia is a member of the Visa Waiver Program, so Australians do not need a visa to visit the US. However, flight attendants regularly give immigration forms to passengers who don't need them. Plus, depending on Fischer's position in his father's company, his visit could require a B1 (visitor for business), L1 (intra-company transferee), or E1/E2 (treaty trader/investor) visa.
When Saito uses his teeth to pull the safety pin from a fragmentation grenade (extremely difficult in real life) the safety lever remains in place even after the grenade is thrown several feet into the opening of a vent.
In the beginning when you see the old man sitting at the table, one of his guards brings him a top that they found with Cobb. He sets it down so it leans to the side with the bottom point touching the table. In the next frame, the longer top point is touching the table.
In the cut-away shot of Fischer's Maybach driving up to the foot of the stairs of a private jet during the initial description of the Sydney-LA flight, the car's rear number plate is shown is show as "63-AG-GW" in black on yellow, with the text "NEW SOUTH WALES". While the format and subtext are correct for that Australian state, the actual pattern of the number is not and should instead be "AG-63-GW".
The registration code for Fischer's private jet is shown as "VH-7JL", with the "VH" prefix indicating registry in Australia. However, in reality Australian aircraft registration codes cannot include numbers.
When Cobb and Mal commit suicide in front of the train, they look young, although they have been in limbo for decades. This is deliberate, an artifact of Cobb's happy recollections. A later scene in which he reflects on their life together revisits this shot, and the actors are aged to show Cobb's corrected memory of the events.
When Saito is lying on his back after being shot in the chest, something that looks like a squib is visible under his shirt. Someone mentioned first aid earlier in the scene, so it may be a bandage on his wound.
There are several valid reasons why Robert Fischer didn't bring a bodyguard on the 747 flight. He may like to keep a low profile. He may have thought it wasn't necessary, since he was in a secured first class compartment. Since he'd just become the heir to his father's company, he may not yet have recognized the need for a bodyguard when he traveled in public. Since his being on the 747 flight was a last minute move, very few people would have likely known about it and had very little time to do anything about it, including potential terrorists. Finally, since it turns out his mind was trained by another extractor, Fischer knew how to protect his subconscious if he ever was put under.
Even though it is not a legal requirement, some U.S Immigration officers will still occasionally stamp passports of U.S. citizens as shown when Dom reenters the U.S at LAX. Additionally, since the movie takes place sometime in the future, it is possible that the policy has changed.