Alden's dog "Duke" is a "meat mouth" Shar-Pei. This variation of the breed did not become common until after Shar-Pei had been brought to the U.S. in the 1960s, more than ten years after the events in this film are set.
Before the end titles, we are treated to headlines in The Times from the 1950s, over Fowler's byline. The variant "advisor" is seen instead of the more traditional "adviser", which was (and still is) prescribed by The Times' style guide - although "advisor" had occasionally appeared since at least 1833.
Alden shows Phuong a picture of Fanueuil Hall in Boston and says, "This is Fanway Hall". Sounds like Fenway Hall. Bostonians say 'Fanyel" hall, or less often, 'Fan-you-well' hall. Fenway Park is where the Red Sox play, so named because is is near the Fens, a marshy area off the Charles river. Fenway has nothing to do with Faneuil.
(at around 28 mins) While Thomas Fowler is typing, we can see his articles printed in The Times; first article on Friday 7 May 1954 starts "After fifty-six days under siege a cease-fire..." Second article on Wednesday 21 July 1954 starts just the same, "After fifty-six days under siege a cease-fire..."
When Pyle is coming to visit Fowler in his apartment for the final time, his dog supposedly leaves a footprint in wet cement which is a clue for the detective. In the scene shown, the dog never touches the cement (his paw lands on a nearby tile).
Following the dinner at Arc en Ciel (around 21st minute) , Michael Caine and Brendan Fraser goes out of the restaurant and chat there shortly. An extra woman waiting on the other side of the street makes it so obvious that she has to walk only after the 2 men walk a few steps in front of the restaurant. It lowers down the natural flow of the scene.
When Fowler is reading his report of the massacre in The
Times, the text says "120 kilometers". In the unlikely event that an English journalist in the 1950s would use kilometers instead of miles, he would have spelled it "kilometres". Also, the text reads that Phat Diem is "120 kilometers north of Hanoi" when, in fact, it is 120 kilometers SOUTH of Hanoi.