Factual error: In the scene after Chan and Wilson crash their car into Stonehenge they walk away and the view is of a field and a beautiful blue sky. In the sky you can see an airplane vapour trail up on the left hand side of the screen. There were no airliners in 1890. (00:58:50)
Factual error: In the scene where the English police come to Madame Tussaud's Wax Museum, they are waving flashlights, which are seen when they exit the museum. The film is set in 1887; the flashlight wasn't invented until 1898 (according to About.com). (01:19:45)
Factual error: The first Kinetoscope (arcade of 'personal movie viewers') was opened in 1894 and the first motion picture studio was located in New Jersey. There is no way that they would have known enough about motion pictures in 1887 to go into them, let alone go to Hollywood to do so. And the use of the word 'movie' is at least twenty years too early.
Factual error: Everyone is abuzz about Jack The Ripper. The setting, however, is around the time of the Queen's Jubilee, which was 20-21 June 1887. Jack The Ripper did not become known to the public until September 1888.
Factual error: The young pickpocket is revealed at the end to be the actor Charlie Chaplin as a child. The film takes place around the time of the Queen's Jubilee in June of 1887. Charlie Chaplin wasn't born until April 16th 1889.
Factual error: Several real-life events are off in the movie's timeline. The movie itself is set in 1887, yet it includes Arthur Conan Doyle beginning writing Sherlock Holmes, although he did so before 1887; a mention of the Savoy Hotel, which was not built until 1889; and many references to and an appearance from Jack the Ripper, who was not active until 1888.
Factual error: Near the start, we see a long shot of New York Harbor, where we can see the Statue of Liberty under construction. When we see the statue it's green, which comes from the statue corroding, which it hasn't had time to do.
Factual error: Chon Wang and Roy O'Bannon crash their car into Stonehenge. In the shot where you see them walking away from Stonehenge, the landmark is shown on a hill. In reality, Stonehenge is on a flat plain.
Factual error: The red coated British Guards are always shown armed with No. 4 Lee-Enfield rifles. The film is set in 1887 - the No. 4 rifle did not come into use until WW2.
Factual error: When Chan and Wilson hitchhike, they stick out their thumbs to catch a ride from a buggy. Hitchhiking in this way wasn't popular until the 1930's; the movie is set in the 1880's.
Factual error: In the scene where Owen Wilson and Jackie Chan confront the street urchin who stole Wilson's watch, Wilson tells him they have "parents who love us", but as he says it he is looking over way over the boy's head. [If you watch the outtakes, Owen Wilson says he feels "so mean" talking to a child that way, so it's possible he simply couldn't be that mean to a child while looking him in the eye. Or he could have been trying to keep from laughing. Either way, it's still a valid mistake, this is just a possible explanation.]
Factual error: During the scene when they are about to try to drown Jackie & Owen you can see the ceiling. On it are large shop lights. Even though lights were invented over 50 years beforehand, lights that new looking and of that kind were not.
Factual error: In the fight scene where Jackie Chan and Donnie Yen fight on the boat right after Yen starts firing the gatling gun, Chan kicks him away from the gun and the gun keeps going. A gatling gun stops firing when the trigger is released, and a new gun such as that one isn't going to have problems with it "sticking" down.
Factual error: Before he became the famous writer, Arthur Conan Doyle was an ophthalmologist, not a detective.
Factual error: In one of the first shots of London, there is an aerial view of the River Thames that shows the bridge leading to Big Ben and father upstream Tower Bridge. 2 problems: the movie is set in 1887 and Tower Bridge was not finished until the year 1894, and secondly, from that shot, Tower Bridge would be below Big Ben, off screen, not above it.
Factual error: It is British law that a non-British (or Commonwealth nowadays) citizen does not receive the title of "sir" as part of their knighthood. Therefore, Chon and Roy would not be referred to in this manner during the knighthood ceremony.
Factual error: All the cars used in the film have pneumatic tyres. The film is set in 1887 and pneumatic tyres were not successfully used on cars until 1895.
Factual error: Early, rotating-barrel machine guns were all activated by cranks, not buttons or triggers as shown in the film. While there were prototypes of trigger-type machine guns such as the Maxim, under development at the time, they were very different in operation than the Gatling-type gun used in this movie.
Answer: The song is "My Generation" performed by The Who.
moviemogul