The role of Amy Robbins went to Mary Steenburgen. However, the studio had wanted Sally Field. Director Nicholas Meyer's first choice was his girlfriend, Shelley Hack. She reportedly didn't want to become famous due to her boyfriend - but she did accept a small role as a docent at the museum H.G. Wells transports into.
When H.G. Wells gives a false name to the police, he uses "Sherlock Holmes". And one of the police officers is named Inspector Gregson, a character from the original Sherlock Holmes stories. Also, director Nicholas Meyer wrote The Seven-Per-Cent Solution, which is considered to be one of the best Sherlock Holmes story not written by Sir Arthur Conan Doyle.
H.G. Wells always refers to his time machine simply as "the time machine" or "the machine". When the machine is first shown, however, the name "Argo" is visible on the front. This is the name Wells gave to his machine in the novel that inspired the film.
Nicholas Meyer's first choice to play the Ripper was Edward Fox. Mick Jagger also considered for the part, but Meyer couldn't see Mick Jagger convincingly playing a Harley Street surgeon.
During chase scenes at the hotel, David Warner is replaced with a stunt double for far shots because he was still on the mend from two broken ankles. In close-up shots, he can be seen running very carefully as not to hurt himself. Also, for scenes where Malcolm McDowell is running through the columns, he is also replaced with a double because of a sprained ankle.
Wells's landlady is named "Mrs. Turner." Sherlock Holmes refers to his landlady as "Mrs. Turner" once (in "A Scandal in Bohemia") even though her name is "Mrs. Hudson" in all the other stories. Nicholas Meyer, a Holmes aficionado and author of three well-known Holmes pastiches, is familiar with this inconsistency in the Holmes canon (he even mentions it at one point in his DVD commentary on Star Trek II: The Wrath of Khan) and apparently included it as an inside joke, along with the several other Holmes references in the film.
The movie theater where Wells and Amy see the film was the same one which showed The Exorcist in an exclusive engagement. The infamous San Francisco serial killer, Zodiac, saw the film there, too.
The trivia items below may give away important plot points.
Stevenson commits six murders over the course of the film - one in 1893 London and five in 1979 San Francisco. The film itself takes place over a little less than a week, from the perspective of H.G. Wells and Stevenson. The historical Jack the Ripper killed a total of five women over the course of 11 weeks in 1888.