Blooper

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.

After Joe throws his drink on Irving, a visible wet mark appears on Irving's shirt. In the next shot, the wetness appears to have disappeared (this occurs twice during the scene).

When Ann is sitting on the banister in front of the clock tower, her cone has a large scoop of gelato, but when Joe arrives a moment later and sits beside her, the gelato is almost gone.

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.

As Ann surreptitiously speeds away from the embassy, stowed away in the back of a delivery truck, the crates that she hides behind change.

When Joe and Irving are first seen, 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.

At the flower stand, the man says "mille lire"(1 thousand), but then says in English "five thousand".

When Joe Bradley follows Ann through the streets, people can be seen watching the filming rather than acting natural.

When riding a scooter or bike, one leans to the inside of the curve of the road, and not the opposite as it appears when the couple are in the scooter shots, especially on the photos selling around the Rome tourist shops. It then is obvious they're riding at the back of some 4-wheeled vehicle.

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.

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 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 - 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 actually was 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 unphotographed first blow with the guitar, not of the second blow, the only photo Irving was actually seen taking.

After Joe rolls Ann out of his bed onto the couch, Ann mumbles, "So happy." However, her mouth doesn't move.

When Ann and Joe are on the scooter, her words don't match her mouth.

When Princess Ann is sneaking out, as she's leaving the room full of mirrors, someone's head becomes visible in the lower left of the screen.

Near the start, Hennessey bets Bradley $500 that he won't get the story and says if he loses, he will owe him $1000 (presumably the extra $500 is from a previous gambling debt). Later when Bradley reveals he did not get the story, Hennessy tells him, "You owe me 500 bucks."