The Vienna Police Dept. has a special unit that is assigned solely to patrol the city's intricate sewer system, as its network of interlocking tunnels make great hiding places for criminals on the run from the law, stolen property, drugs, etc. The "actors" playing police officers in the film were actually off-duty members of that unit.

Orson Welles worked one week on this film.

A huge fan of the film, Martin Scorsese wrote a major thesis on it while in film school. He got a B+ for it, his tutor remarking "Forget it, it's just a thriller".

In Vienna the film has a permanent slot in one of its oldest cinemas. It is playing three times a week in the famous "Burgkino".

During meetings between Graham Greene and Sir Carol Reed with David O. Selznick, Greene was less than impressed with Selznick, who had (according to Selznick's own son) "become something of a parody of himself". Greene later mocked Selznick's dependency, at that stage, on the drug Benzedrine, better known as "speed". Reed also became hooked on Benzedrine while shooting the time-consuming film. Both Reed and Selznick were operating on as little as two hours of sleep a day.

Continuity

Three cats were used for Harry Lime's only loved cat, but all three cats were different sizes and colors.

When Calloway and the police stand waiting for Harry to arrive at the station, an elderly balloon man tries to sell them a balloon. His balloons have designs printed on them. Calloway has his sergeant buy one to get rid of the old man, but the balloon has no printing on it, as the shot of the police was filmed later in London.

In the sewer, before putting his fingers through the grate, Harry Lime holds the stair's supporting pole with his right hand, but the gun should be in his hand, as displayed before and after this shot.

Harry Lime's sewer scenes were shot in two locations--at a studio in the UK and on location underground in the Vienna sewer system. In the Vienna sewer location scenes Harry's breath is visible (it was cold down there); in the sewer scenes shot in the UK studio his breaths are not visible.

The dog and the book briefly change between Kurtz' two hands when he is being shown where Lime was hit by a truck.



Factual errors

The line about the cuckoo clock being Switzerland's only contribution to culture is factually incorrect: the cuckoo clock comes from the Black Forest, across the border in southwestern Germany.

The opening narration points out that post-war Vienna was policed by an international force of the four powers, namely the British, French, Americans, and Russians, "and none of them speaking the same language." Obviously, both the British and Americans spoke English.



Revealing mistakes

In the two separate back projection shots of Calloway, Martins and Paine, supposedly traveling in a jeep at night in Vienna, a double-decker London bus can be seen in the background.

When Harry opens the lid to the sewer after being chased by the police, "Buchdruckerei' signboard is in the background. When supporting troops arrive and open a lid of another sewer, the same signboard "Buchdruckerei' is seen, meaning that they shot two scenes at the same place.



Miscellaneous

At 1:21:58 in the film, as Trevor Howard says, "I'm beginning to know Lime", there is a brief shot of what is supposed to be a dossier on Harry Lime with two photos of a tousle-haired grinning Orson Welles. Freeze-frame on the shot and the page is actually a studio production notes sheet marked "Script Report" dated 4-3-48 with columns listing Scenes Taken, Added Scenes and Retake Scenes, plus boxes for listing Staff, Cast, Speaking Bits, Action Props and Effects.

In the cover of Anna's passport the name of the country in French is misspelled as "Autreich" instead of "Autriche".



Anachronisms

In the final scenes as Anna walks down a long avenue of trees barren of leaves in the winter season, a flurry of leaves showers down dramatically in the foreground.



Audio/visual unsynchronized

When Holly Martins first encounters Harry Lime across the street in a darkened doorway, he doesn't know who it is and he yells out, "What kind of a spy do you think you are satchel foot?" When he says this line, it is clearly visible that he is not saying anything at all.

After Calloway has shown Martins the evidence against Lime, Calloway picks up the phone. We hear his line, "Get me police headquarters," but we don't see his lips move.



Errors in geography

Upon arriving in Vienna, Martins says that he will be staying with Lime at Stiftgasse 15, which is in the Josefstadt section of the city. Lime's apartment, though, is located at Josefplatz 5 in the city's central district, directly across the street from the statue of Emperor Joseph II and about a mile away from Stiftgasse 15.



Plot holes

Holly Martins quizzes Popescu about a man named Joseph Harbin but he only learns of Harbin's existence from Maj Calloway later in the film.



Character error

Martins incorrectly calls Dr. Winkel "Winkel" instead of the correct "Vinkel", even though he has only heard the name (pronounced "Vinkel") and not seen it written at all.

It is unthinkable that a major would say to a colonel (who outranks him): 'What is it, Brodsky?'