Ann wears a white tie until she sits down on the Spanish steps. The tie is gone and the collar is open when Joe speaks to her on the next shot. When they are stopped at the Palazzo Venezia, Ann is wearing a striped neckerchief and continues to do so for the rest of the evening.
Still in Joe's apartment, when Mr. Hennessy is finishing his speech to him, Joe is holding the envelope with both hands in front of his body. In the next shot, when Mr. Hennessy leaves, Joe is holding the envelope with his right hand leaning on his hip.
When the princess and Joe Bradley stand in front of the magistrate after the scooter incident, her blouse is dirty and so is her face. When they come out of the police station, her blouse is spotless and so is her face. She could conceivably have washed her face in the interim, but there would not have been an occasion in 1953 to clean and dry a blouse that quickly.
When Princess Ann accepts her change from the Gelato salesman, she is holding the Gelato in her right hand and puts the change in her left pocket. Immediately afterward, when the flower salesman is trying to sell her flowers, she shows him that she has very little change left. When she does this, she takes it out of her right pocket, not her left where she had just put the money and she is holding the Gelato in her left hand.
When Joe is saying farewell to Princess Ann when she first leaves his apartment, he places his hand on the door handle. In the next shot, his hand is at his side and he then places it on the door handle again.
When we see, for the first time, the truck where the princess is escaping the palace, there is a Cinzano box inside, but when Anne climbs into the back of the truck, the brand "Cinzano" is not seen any more and another brand appears instead.
After Joe returns to his apartment upon finding out from his boss that Princess Ann is sleeping there, he straightens the bed, moves the pillow, and moves Ann from the couch back to the bed. In the process of tidying his apartment, he moves his alarm clock to the center of the top of the bed's headboard. In the scenes following while Ann awakes, as the camera cuts back and forth, the clock changes places back and forth from the center to the left on the headboard.
After her haircut, when Ann enters the piazza, clock tower 1 reads 12:35 pm, but when Joe follows behind her, it reads 12:32 pm. When Ann sits in front of clock tower 1 in medium shot and Joe "runs into her", it reads 2:40 pm, even though it's only been a few minutes between entering, getting gelato and sitting down. Their conversation starts at 2:40 pm, but during the close-ups of Joe, clock tower 2 behind his head reads from about 4:55 pm - 4:58 pm, and when he stands up at the end of conversation and says "Today's going to be a holiday", clock tower 1 behind them in the medium shot reads 3:50 pm.
After Ann leaves Joe's apartment, when she looks in the salon window her tie is on and cuffs are buttoned, but when she sits down in the hair salon chair, her cuffs are rolled up slightly. When she leaves the salon her cuffs are rolled up slightly, but when she approaches the gelato stand, her sleeves have been rolled up to mid-bicep. She sits down on the banister with her gelato, tie on, but a moment later the tie is gone (and never returns) and her top blouse buttons are open. Through their tour of the Coliseum, Ann's neck is bare, but on the scooter ride leaving the Coliseum a striped scarf appears mysteriously around her neck. In the car as Joe drives Ann back to the palace, both the striped scarf and tie are missing.
When Princess Anne wakes up in Joe's apartment, during their conversation she asks what time it is and Joe replies, "About one thirty." However, after she leaves the apartment, walks to the Trevi fountain, has her hair cut, then goes to the Spanish Steps, the clock tower behind her reads 12:35.
When we first see Joe and Irving, they are playing five-card draw poker. There are eight men at the table playing, but it is not possible to play five-card draw poker with eight players. After the initial deal, there would only be twelve cards remaining for the draw, not enough for everyone to draw up to the three cards allowable in such a game. They could only play five-card stud. Interestingly, when Joe leaves the table, the dealer calls for seven-card stud, which is the only game playable with the seven remaining players.
The black ink in the Roman newspapers reporting the illness of Princess Ann is glossy and the paper is slick, indicating that they are short-run items from a small business-style printer use by the prop department, rather than being a normal newspaper. This issue with glossy black print continued for decades in movies, finally ending with the introduction in recent years of non-glossy inkjet ink.
It is a known fact that when riding a scooter or bike, one leans to the inside of the curve of the road, and not the opposite as it appears in the scene of the couple in the scooter shots, especially on the photos selling around the Rome tourist shops. It is then clearly obvious they're riding at the back of some 4 wheeled vehicle.
The photo Irving takes during the fight at the dance, of Ann smashing the secret service agent over the head with the guitar, is not the one taken at the moment indicated in the film and shown later as the photograph. Supposedly, when Ann first hits the agent, Irving has missed it and calls out for "Smitty" (Ann) to hit him again - and Ann obliges, striking the agent on the head a second time as Irving shoots the picture. But a look at the subsequent photo clearly shows that it was in fact taken at the moment of the first blow, not the second. In the action, when Ann hits the agent the second time, the guitar appears already broken, and the agent is turned almost 180 degrees away from Ann's face and is already sinking down from the first blow, his face barely visible. But the photo - supposedly the only one Irving got - clearly is of the first, not second, blow. There, in both the live action and the photo, the agent is facing to his left and has not sunk so far down, his face is mostly visible, and the guitar is not as damaged as in the second blow. That the photo was actually taken of the first blow is further indicated by a close viewing of the live action of Ann hitting the agent the first time. At the moment of impact the film has a brief jump-cut, indicating that a frame has been deleted from the film, and in addition the tail-end of a flash from a camera's flashbulb can be seen very briefly immediately after the cut frame. The missing film frame coincides exactly with the instant Ann hits the agent with the guitar, and is the identical shot that was used as Irving's "photograph", which he later presents to Ann in the packet of pictures he'd taken. But it's a photo of the supposedly un-photographed first blow with the guitar, not of the second blow, the only photo Irving was actually seen taking.