Some pathologists conducted a study determining how long a person lasts before dying after being stabbed directly. A scene from the film where Hamlet kills Polonius was also viewed as reference to their study. In the end, it was found that a person, after being stabbed directly, can only last long enough to utter four words. This means that Polonius's uttering of the words "O, I am slain" as he dies is medically possible.
Kenneth Branagh offered Gérard Depardieu a small part in the four-hour version of the film out of gratitude for his active support on the release of his first feature Henry V (1989) in France (not only was he the main distributor of the film but also dubbed Branagh's voice on the French version).
Kenneth Branagh's decision to shoot in 65mm was largely inspired by a film format seminar conducted by visual consultant Rob Hummel. Hummel convinced him to use the format because of high-resolution and certain shots could only be achieved in 65mm. Also, Branagh once said that the intention was to give a sweeping feel to the play, hearkening back to the 1960s - epics like Lawrence of Arabia (1962).
For more than a year, Kenneth Branagh had tried shopping the project around major studios in Hollywood, but no studio was willing to finance a four-hour production, citing skepticism of the commercial viability of a William Shakespeare adaptation to a late 20th-century audience. Also, most studios were aware of the negative reviews and the commercial failure of Branagh's previously-directed film, Mary Shelley's Frankenstein (1994) and some of them would only finance the film if the content and the budget is cut to half. However, Castle Rock Entertainment, agreed to finance the film and to Branagh's demands (filming in 65mm, complete control over the film, etc..) under two conditions: a star-studded cast for the show and a 35mm, abridged 2.5 hour version of the film for a wider release.
One of William Shakespeare's lines is actually changed with no acknowledgment. The sorrows come line "O Gertrude, Gertrude, when sorrows come they come not as single spies, but in battalions" becomes simply "When sorrows come they come not as single spies, but in battalions," probably because Claudius delivers them in voiceover and we do not know to whom he is speaking. It is the only line in the film that is changed because of the way the scene is filmed.
The title of Hamlet's play-within-a-play is "The Murder of Gonzago", which may or may not have been extrapolated from an Italian prose work. However, when asked its title by Claudius, Hamlet responds by bestowing on it a new moniker, which reflects its purpose (to "catch the conscience of the King") - he calls it "The Mousetrap".
The construction of the interiors of the "Elsinore Castle" set (actually Blenheim Palace) cost two million dollars alone. The exteriors are simply the exteriors of the palace and had already been standing since 1784.
Kenneth Branagh first encountered the full length version of the play while performing in the 1992 BBC Radio production of the play with co-stars Derek Jacobi and Richard Briers (who would reprise their roles as Claudius and Polonius respectively in the film). This radio performance anticipated the winter 1992 full text production of Hamlet by the Royal Shakespeare company - the one that would finally crystallize Branagh's interpretation of the character and lead to the film.
Hugh Crumwell was the then-principal of the RADA in which Kenneth Branagh studied. Crumwell was on the set all the time; he came as a request by Branagh to give an objective critique for the performance of each take.
Like others before him who simultaneously acted and directed a film, Kenneth Branagh used an acting double, Orlando Seale to play Hamlet during camera set-ups and rehearsals. This means Seale had to learn and perform almost the entire play with the entire cast, yet only appears on screen as an extra, playing the part of a 'Boatman'.
Cast members Kenneth Branagh, Derek Jacobi, and Gérard Depardieu have all played Cyrano de Bergerac. As translated into English by Anthony Burgess, in the speech where Cyrano rattles off a list of possible insults to his nose, he includes "Oh that this too, too solid nose would melt," a parody of the "too, too solid flesh" line from this play. (In the Brian Hooker translation of "Cyrano", which José Ferrer played onstage and on film, the line is given as "Was this the nose that launched a thousand ships?", a parody of "Was this the face that launched a thousand ships", a line from Christopher Marlowe's "Doctor Faustus".)
The was the first British film to be shot in 65mm since David Lean's Ryan's Daughter (1970), in which John Mills, was made in Ireland 26 years earlier. In the interim, Far and Away (1992) (also shot in 65mm in Ireland) was a Hollywood production on location.
John Mills (Old Norway) and Richard Attenborough (The English Ambassador) were offered the roles of the murderers in Richard III (1955), in which John Gielgud (Priam) played the Duke of Clarence. However, Mills believed that it would be stunt casting and Attenborough was unavailable.