Ariane washes her hair and is rubbing it with a towel just after Frank Flannagan leaves her apartment. Moments later, her hair is completely dry and perfectly styled.
While in a fit of outrage, Monsieur X rips the 'Do Not Disturb' sign off the door knob. Leaving the suite, he stoops and picks up the now complete sign and places it upon the door knob.
Early in the film, Chavasse demonstrates that he knows the song "Fascination," even singing it for Monsieur X. Later, he needs to be told what it is, several times.
In the final scene at the train station, the sign says that the train for Nice is at 17:00 (5:00). After the train has left, when Frank Flannagan kisses Ariane in the compartment, the time on his watch reads 2:55.
When Flannagan drinks himself into oblivion hearing Ariane's list of men she pretends to have had, he lets the bathtub run over - and very much so. Some time later he leaves the hotel room with his gypsy band, and we see the bathtub empty with no signs of a flood, and it is never mentioned again.
Claude begins the film spying on Frank on Monday, June 11th, which is a correct day and date if the year is 1956. At the end of the film, it is the next year and Claude mentions a date of Monday, August 24th. However, August 24th, 1957 was a Saturday. Furthermore, there are normally 439 days between June 11th of one year and August 24th of the following year. If the second year is a leap year, the span is 440 days. Since neither 439 nor 440 are evenly divisible by 7, it is impossible for June 11th of one year and August 24th of the next year to both be Mondays.
When Ariane returns one of her father's files to a locked safe and opens it by banging it with her fist, a thin wire used to pull open the safe is visible.
The text of the Japanese newspaper article with the photo of Frank has nothing to do with the plot of the movie - it reads "King Kane is Dead," as it was borrowed from Citizen Kane (1941).
When the gypsy musicians are playing for Flannagan in the Turkish bath, the lead violinist discovers that the condensation has made his instrument fill up with water, tips it out, and continues playing: the sound is unaltered.
During the opening "Parisians making love any time, any place" montage, the two,"statues" in the background at the museum are clearly painted cardboard cut outs.
At 1 hour 53 minutes, when Flannagan says to Chavasse, "I couldn't get to first base with her!", Gary Cooper clearly mouths something else.