Goofs

At the hot dog stand the top of a Tabasco bottle is seen above the napkin holder. Then it disappears and Ralph has to go to the counter and ask for the Tabasco.

When in the Portrait Gallery the painting of the 2nd Duke of Warren reverses between close-ups and distance shots.

Near the beginning, when Duncan is explaining Ralph's heritage to him at the hotdog stand, one of the soda glasses alternates between being upright and being slightly tipped between shots.

Ralph's hand on his own face changes position between shots as he is being addressed regally in his dressing room.

The "punks" who are shown watching television and commenting at various times throughout the months-long reign of King Ralph are always wearing the same clothing.

Ralph is repeatedly referred to as the King of England. The Kingdom of England ceased to exist in 1707 during the reign of Queen Anne, following the Act of Union between England and Scotland. Therefore the last King of England would have been King William III. The correct title would be "King of the United Kingdom" (for short) or "King of the United Kingdom and the other Commonwealth realms" (in full).

While this movie is fictional, King Ralph and King Cedric would not be titled as Ralph I and Cedric I. They are only numbered as such once there has been a second monarch of the same name. Hence Queen Victoria is not referred to as "Victoria I."

The Prime Minister and Lord Percival refer to the house of Wyndham (Windsor) and then indicate that the next in line for succession would be descendants of the house of Stuart, of which Lord Percival is one. The next house in line for succession would in fact be the Hanoverians.

In the establishing shot of Buckingham Palace at the beginning of the film, no Royal Standard is seen flying above the palace, which would signify that the monarch is in residence. Immediately following the establishing shot, it is shown that the monarch is, indeed, in residence and thus, the Royal Standard should be flying.

After Ralph asks about pay, he is told that he doesn't get a 'salary' as such, and later he is unable to pay for food at Burger King stating that he hadn't been paid yet. This is actually false, as the monarch is entitled to the Privy Purse, which is the personal income of the monarch. Ralph should have been immediately made a millionaire.

The same actor is shown portraying a food server during the dinner scene and then again as a policeman when Lord Hargrave is arrested.

The name of Finland's King is Gustav. "Gustav" is a Swedish name.

When Ralph and Miranda were kissing in the park, the paparazzo's camera flash did not go off as he took the photo.

During the performance of "Good Golly, Miss Molly", the harpsichord music continues to play when Ralph's fingers are not touching the keys. This is most noticeable when he is dancing with Miranda and just before the performance ends.

While the film states that the entire British royal family had been killed and an heir cannot be located, the actual line of succession to the British throne extends to hundreds of nobles and other monarchs throughout Central and Western Europe. An even longer, extended list tracing the royal family as far back as 1800 extends into thousands of possible heirs. Thus, even if the immediate British royal family were to die, there would be many people left in the line of succession who would not have been in the country.

Under English law, any child born to a royal out of wedlock is ineligible to succeed the throne, which extends to the child's heirs. This can never be reversed, even if the child is legitimated by the Royal parent. Therefore, despite being the "only" surviving member of the Windham line, Ralph could never take the throne since his father was born out of wedlock. The same law against illegitimate-line heirs would apply to Cedric.