According to an interview with John Goodman in the article "'No Leading Man, King Ralph Insists" published in the February 12, 1991 edition of the Los Angeles Times, Goodman denied his new leading man status in this movie, and said he was still just a character actor. Goodman said: "Don't call me a leading man. This is just another part, with a lot more lines. The only difference for me this time, was that I didn't have time to fool around when I wasn't working. When you're the leading man, your meter's running all the time, and you're always working. There's no goof-off time. But that still doesn't make me a leading man. I'm still just a character actor. Nobody's ready to call me Mel Gibson, Jr., and I don't think anybody's ready to pay good money to see me get the girl in the movie. I know I wouldn't go see something like that."

John Goodman does his own singing.

During the film, King Ralph and Miranda go to a Burger King, where Ralph fails to get a Whopper. One of John Goodman's first acting jobs was in a commercial for Burger King, where he happily consumes a Whopper.

The script was originally written with Bill Murray in mind.

Although Finland is not in reality a monarchy, it almost became one after independence was declared in 1917. Even a prospective King was chosen, but later, the idea fell out of favor, and a republic was created instead. Since the film clearly happens in a slightly different alternate history, the appearance of the Finnish Royal family should not be considered a goof, but a rather erudite touch from the filmmakers.

The film was released eleven years after its source novel, "Headlong" by Emlyn Williams, had been published.

First top-billed starring role of John Goodman. On movie posters, the part was also Goodman's first sole name-above-the-title billing.

John Goodman was the only American actor in the movie's lead cast. The rest were British actors.

John Goodman began work on the film shortly after the television sitcom Roseanne (1988) had just finished production on the second season.

The line of dialogue which described King Ralph as being Ralph the Chicken-hearted was a spoof of medieval British monarch Richard the Lionheart.

In the beginning of the movie, in the scene where Ralph (John Goodman) is in the dressing room getting fired, he says, "What? 'Cause I wouldn't sing 'The Impossible Dream'?" This is a reference to Peter O'Toole (Sir Cedric Willingham). In Man of La Mancha (1972), Peter O'Toole sang the song "The Impossible Dream".

King Ralph cracking nuts with the Seal of England is a reference to Mark Twain's The Prince And The Pauper, in which Tom Canty (the pauper) uses the Seal to crack nuts that he snuck into his room.

When Princess Anna of Finland (Joely Richardson) is first seen, due to her look and clothes, she resembles Princess Diana.

In the novel "Headlong" by Emlyn Williams, the Ralph Jones (John Goodman) character was known as Jack Green, becoming King John II, instead of King Ralph. The character of private secretary Sir Cedric Charles Willingham (Peter O'Toole) was known as William "Willie" Millingham in the book, while the character of cabinet secretary Lord Percival Graves (John Hurt) was called, in the novel, Sir Godwin Rodd, and nicknamed "Sir God".

The picture was not selected to be the Royal Performance Film in 1991. The honored movie selected for that year when this movie debuted was ironically another American comedy, Hot Shots! - Die Mutter aller Filme (1991).

Clarke Fountain at Allmovie states that the type of heir that Ralph Jones (John Goodman) is in this film, is a "collateral heir". Fountain writes that "Sometimes a family title, among the nobility of England, goes to the "collateral" heirs, people not in the direct line of decent, like cousins, great-nephews and the like. On rare occasions, these people are not even aware that they are about to be elevated to the House of Lords, and they have been living more-or-less ordinary lives. In this comedy, the family which lacks direct heirs is the Royal Family of England, as all of the likely heirs have died one after the other in swift succession."

The movie was filmed during April, May, June, and July 1990.

Peter O'Toole previously played British Monarch Henry II in Becket (1964) and Der Löwe im Winter (1968).

The name of the African country was "Zambezi". It is fictitious, though ironically, Zambezia - In jedem steckt ein kleiner Held (2012) had a similarly titled name, which refers to that film's fictitious African bird city. Moreover, there is an African place called "Zambezi", but it is not a country. Wikipedia states, "The Zambezi (also spelled Zambeze and Zambesi) is the fourth-longest river in Africa, and the largest flowing into the Indian Ocean from Africa. The 2,574-kilometer-long river (1,599 miles) has its source in Zambia, and flows through eastern Angola, along the eastern border of Namibia and the northern border of Botswana, then along the border between Zambia and Zimbabwe to Mozambique, where it crosses that country to empty into the Indian Ocean."

One of two 1991 movies starring John Goodman. The other picture was Barton Fink (1991).

This was Dallas Adams' final film before his death on August 29, 1991, at the age of forty-four.

The first of three queenly movie roles for Judy Parfitt. She also played Queen Marie in Auf immer und ewig (1998) and Queen Mary in W. E. - Die Romanze des Jahrhunderts (2011). She also played Queen Lillian White in the television series The Charmings (1987).

The film is loosely based on the 1980 novel "Headlong" by Emlyn Williams. Both Williams and Sir John Hurt (Lord Percival Graves) played the Roman Emperor Caligula in adaptations of Robert Graves' 1934 novel "I, Claudius": Williams in the unfinished film I, Claudius (1937), and Hurt in Ich, Claudius, Kaiser & Gott (1976).

The name of the rock band seen at the end of the movie was "Ralph and the Dukettes".

The film takes place from March to July 1990.

Many of the main cast had first names starting with the letter "J". These were John Goodman, Sir John Hurt, Julian Glover, Joely Richardson, James Villiers, Judy Parfitt, and Jack Smethurst.

Peter O'Toole and James Villiers, who were friends since they met as students at the Royal Academy of Dramatic Arts in London in the early 1950s, have previously appeared together in The Ruling Class (1972).

The dogs, with which King Ralph is attempting to play fetch, are a reference to Queen Elizabeth II. She prefers the Pembroke Welsh Corgi breed, and has owned more than thirty during her reign.

Star Billing: John Goodman (first), Peter O'Toole (second), and Sir John Hurt (third).

The name of the Las Vegas ape was "Mitzi the Psychic Chimp".

Julian Glover (King Gustav of Finland) once played the James Bond villain Kristatos in James Bond 007 - In tödlicher Mission (1981). The name of the Bond villain in James Bond 007 - Stirb an einem anderen Tag (2002) was called Gustav Graves. There is also a character called Graves (played by Sir John Hurt) in King Ralph (1991). James Villiers, who played Prime Minister Jeffrey Hale in this movie, also appeared in James Bond 007 - In tödlicher Mission (1981).

According to "Variety", on this picture "Lensing was done on UK locations, and at London's Pinewood Studios."

The amount of the payoff to Miranda Green (Camille Coduri) was fifteen thousand British pounds.

Despite prominent billing in the opening credits, Judy Parfitt (Queen Katherine of Finland) has only one line.

When Lord Graves knocks on Miranda's door a picture of U2 can be seen on the back of the door showing Bono and The Edge.

The Treason Act of 1702, by which Ralph has Lord Percival Graves arrested, is an actual Act of Parliment, enacted in the last year of William the Third's reign. It made it a capital offense to attempt to prevent the successor to the crown from properly taking the throne. Eventually, in 1998, the punishment was changed from death to life imprisonment.

The real royal family name, Windsor, was changed to the fictional name Windham for the movie. Un-synched lip movements in a few parts (most notably the abdication scene) seem to suggest the change was made after the film was shot.

The title that Ralph Jones (John Goodman) was knighted with at the end of the film, was the "Third Duke of Warren".

Ralph Jones' (John Goodman's) full name after he received his title, was "Ralph Hampton Gainesworth Jones".

When private secretary Sir Cedric Charles Willingham (Peter O'Toole) is crowned King Cedric I at the end of the film, though fictitious, it became the third time in motion pictures that O'Toole had played an English Monarch. O'Toole portrayed King Henry II in Becket (1964) and Der Löwe im Winter (1968).

In the picture's source novel "Headlong" by Emlyn Williams, the character equivalent of private secretary Sir Cedric Charles Willingham (Peter O'Toole), William "Willie" Millingham, is crowned King William V at the end of the book, which was first published in 1980 about two years before Prince William was born in 1982. Assuming William one day becomes King of England, and that he is likely to take the title of William V, this will be the same "William V" monarch title that William Millingham is called in this film's source novel.

King Ralph's (John Goodman's) title was Ralph I or Ralph the 1st. His baby son was affectionately billed in the credits as Ralph II.

Early in the film, the entire British Royal Family is wiped out due to an electrocution accident. In the movie's source novel "Headlong" by Emlyn Williams, they are not electrocuted, their cause of death is different. In the film's source book instead, Wikipedia states, "in May 1935, the entire British Royal Family is killed in a freak accident after the explosion of a large dirigible (similar to the Hindenburg disaster)".

As Miranda is about to leave after their first date, she extends her hand first to King Ralph for a hand shake. There is a "no touch" rule for Royalty. The only time a hand shake is appropriate, is if the Royal person first extends their hand.

John Goodman has played the King of England (in this movie) and the President of the United States (on The West Wing (1999)). In both instances, the character was unexpectedly elevated to the high position, and in both instances, the assumption of the high office was temporary.