Factual error: If you take the train from Paris to Cannes you won't pass the Eiffel tower.
Factual error: Roberta has a Meet The Brady Bunch record on her desk. The release date for this record was 1972, yet this film is set in the summer of 1970. (00:12:55)
Factual error: When it's 1969 we see a boy (I'm not sure which one so you'll have to look) riding a Shwinn Sting-Ray Krate Grey. That bike didn't come out until 1971 and they only made them that one year. (00:02:45)
Factual error: At the end, where TS and Brandi are getting married in Universal Studios, the caption mentions it is Universal Studios Florida, the actual scene is filmed on the backlot tour at Universal Studios Hollywood. (01:29:36)
Factual error: The roads show only two wheel tracks, there is no wear on the center of the road, from either horses or oxen. Most pre-auto movies miss this.
Factual error: Not only is the tractor the wrong vintage, it is pulling a round baler that wasn't invented until the 1970's.
Factual error: At the ball, in 1957, they play Eddie Cochran's "C'Mon Everybody" which wasn't written until 1958.
Factual error: When Arthur marries Guinevere, the altar is decorated with yellow hybrid tea roses. Hybrid teas were not developed until the late 19th Century; yellow ones would not have been available in England until approximately the 1950s.
Factual error: John Smith's (voiced by Aussie, Mel Gibson) accent changes and also fades in and out during the course of the movie.
Factual error: When Lucy jumps off the platform to save Peter, and is trying to wake him, the oncoming train blows its whistle. However, the L-trains/subways in Chicago do not have whistles like ground locomotives do.
Factual error: When Sydney arrives at the Christmas Party, President Shepherd and A.J. MacInerney ask where she's been. She says she was stuck at Dupont Circle and they ask why she was on the Hill. But to get from Capitol Hill to the White House, one would not drive anywhere near Dupont Circle.
Factual error: James Graham, 4th Marquess of Montrose, became 1st Duke of Montrose in 1707, six years before the film is set, although the film refers to him throughout as a Marquess.
Factual error: In the movie, it is depicted that Verlaine shoots Rimbaud in the palm; in reality Verlaine shot Rimbaud in the wrist.
Factual error: When asked, Julie Delpy says the reason her English is so good is because she spent a summer in LA. Come on. Even after a year, almost no one could manage to speak and pronounce a foreign language that well, let alone in a summer. Her English is very nearly flawless. We know she has spent some time in London before, but if she had stayed there long enough to learn to speak such good English, she would have learned it the way they speak it there, which means she would have a British accent and not an American one. Someone - whether or not she's a native speaker - doesn't change accents after spending a mere three months somewhere.
Factual error: At one point in the film, Morgan calls out "Riflemen, to me!". The film is set in the late 17th century. Whilst rifling had been invented prior to this date, it was still rarely used except on the most expensive weapons, and even then mostly used by specialists. It is highly unlikely that all, if any, of the pirates would have been armed with them, especially in the close quarter fighting they would have been expecting. The pirates would be more likely to be armed with the more common smooth bored muskets of the period, so "Musketmen, to me!" would be much more likely to be correct.
Factual error: At a very early point in the film, the King says something along the lines of "....and these are your playmates". In the background is a horde of 17th century ladies boating on the Achille Duchenne water parterre at Blenheim Palace. The palace wasn't built until the late 18th century, and the parterre was not designed until 1925.
Factual error: In the final trial scene, held outdoors in the town center, tribunal members who are on the raised platform are shown sitting by or leaning on tables spread with small, Persian-style carpets. It is likely that the set designer based this choice on an early American painting, which does include many subjects posing with furniture thus bedecked; however, the practice of laying a carpet on a table was employed only when posing for an artist's portrait under particular pricing terms set for a commission. Artists charged their rich patrons based on a scale of bodily detail. The more limbs, the greater the price. (You've no doubt heard the related expression 'to cost an arm and a leg.') A composition from the waist up would be more affordable, but would necessarily exclude a prized carpet, which was an icon of personal affluence. So, the artist adapted and cleverly laid an admired carpet on a desk or table to satisfy the vain, yet thrifty patron.
Factual error: George is paid an extra $15,000 to move out of the house in ten days and he his paid in $1,000 bills. Although $1,000 bills do exist, they are not used by private citizens. They are only used by large banks.
Factual error: When Kitt drops her mom off at the airport, that's not Chicago O'Hare. She is actually dropping her off at BWI airport so Claudia can fly...to Baltimore, Maryland.
Factual error: When Calvin is invited to sit at the table with King Arthur and his daughters, as he is sitting down you can see that King Arthur is wearing a t-shirt under his robe.