When Reggie and Joshua arrive at the stamp market, workers on ladders can be seen starting to put a new cover on the completely roofless Berkeley Café in the background. However, a few minutes later, when Grant runs to catch a cab, the building is directly behind him, and the new roof is long since complete.
When Mrs. Lampert meets Mr. Bartholemew at the American Embassy, the cups that wine is poured into appear and disappear and change positions throughout the scene.
During the funeral service for Charles Lampert, the position of his fingers crossed on his chest changes between when Leopold views the body and when Tex views the body.
When Jean-Louis' mother steers him away from Mrs. Lampert and Peter Joshua his hair is on his forehead, but when he turns to spray Peter Joshua with the water gun his hair is tucked into his beanie.
When Alex and Reggie are on the restaurant boat, a man appears and disappears behind them between shots.
The sign outside the embassy would not read "American Embassy." It would read "Embassy of the United States of America" or "Ambassade des États-Unis d'Amérique."
The rare stamps are said to be valued at $250,000, but wouldn't that have only been in their condition prior to being affixed (glued) to a modern envelope? One could surmise their value was reduced due to their altered state.
Charles' body, thrown from a fast-moving train, could not possibly have fallen straight away from the camera in the opening scene.
During the Seine cruise, the rear projection plates are repeated. The boat passes the same building, the Institut de France, twice - once when Reggie and Joshua are standing and yet again later when they are seated.
Reggie, Joshua, and Bartholomew could not have gotten into the theatre so easily when all theatre exit doors are padlocked from the inside.
When Tex shows Joshua the envelope with the missing stamps, he seems to deliver his lines slightly incorrectly: he first says, "You n- greenhorn!", then says, "You block-headed jackass! You nincompoop", so it appears that he started to say "nincompoop" at the wrong point in the script.
During the night boat scene, the boat passes under a wide bridge, but the lighting on the characters is unaffected, revealing a rear projection special effect.
Bartholomew spent 10 months in a POW camp with untreated bullet wounds in his legs, yet he runs and moves around as well as any average middle-aged man. He even does knee bends while talking to Reggie on the phone.
At the start, an electric train speeds past the camera before the body is thrown from it. The soundtrack gives us the hoot from a steam train.
When Joshua and Scobie are fighting on the rooftop, the supposed brick wall and doorway move when Scobie lands against them.
When Reggie and Peter are walking by the river and he takes the ice cream from her, as he turns around, the inside of his jacket is briefly visible where there is a thin black wire.
Regina, fleeing Canfield, rides the Metro from Saint Jacques (signs prominently seen) to Palais Royal (mentioned several times in dialog). From Saint Jacques one cannot get anywhere near Palais Royal without changing trains at least once; but of course she never does (because Canfield would have another chance to catch her).
When Reggie enters her hotel room, it's pitch black, but Scobie is supposed to have just been ransacking the room looking for the money.
Cruikshank's explanation that Bartholomew had access to the real Bartholomew's office because it was lunchtime is beyond lame. It doesn't explain how Bartholomew knew when lunchtime was and how he bypassed the embassy's security undetected.
At the embassy, Bartholomew tells Reggie that Tex, Scobie, and Gideon are after the money from the auction, which none of them could have known about.
As Reggie and Sylvie are walking around the indoor swimming pool, the boom mic and boom arm are reflected in the glass as they turn the corner.
Scobie is covering "Dyle" with a gun held in his artificial hand/claw, but it wouldn't be threatening as there's no way he would be able to pull the trigger.
When Regina is taken to the morgue to identify her husband's body, the coroner's hands are visible as the body drawer is closed. The coroner's fingers would have prevented the drawer from closing or else his fingers would have been injured.
When Tex places a mirror under the nose of the dead Lampert to see if he's still alive, he does so for only a fraction of a second; this is not enough time to catch someone breathing.
In the opening scenes when Mrs. Lampert is being shot in the face by the water pistol, the hand holding the pistol is obviously an adult and not a little boy.
Joshua says that Juliet was a widow at age 15. However, in the play, Juliet is only 13. Shakespeare never gives him a specific age, but Romeo is believed to be 16. Romeo dies first, making Juliet a widow at age 13; they were married for just 4 days.