Val Kilmer initially accepted his role so that he could work with Marlon Brando. Before filming started Kilmer informed the production that he did not want to be involved in any capacity due to the creative direction of the film, but due to the massive success of Batman Forever (1995) the studio could not afford to let him go and he was forced to participate by contractual obligation.
Assassimon, the baseball bat-wielding ape-creature, seems to be a remnant of an earlier draft of the screenplay where some of the Beast People were putting together a baseball team.
When Edward Douglas is rescued from the life-raft the shadows in the life-raft seem to indicate a different time than would be indicated by the position of the sun behind the rescuing boat. In fact if, as is implied, he can see the rescuing boat, the sun is in two completely different positions in the sky.
Prior to injecting Douglas' I.V., Montgomery places the syringe cover between his teeth. Following the injection, Montgomery retrieves the syringe cover from the bedside table.
Dr. Moreau: Permit me Mr.Douglas, to tell you something of the Devil as I've come to know him. The Devil is that element in human nature, that impels us to destroy and debase.
Dr. Moreau: I have almost achieved perfection you see, of a divine creature that is pure, harmonious, absolutely incapable of any malice. And if in my tinkering I have fallen short of the human form by the snout, claw or hoof, it really is of no great importance. I am closer that you could possibly imagine sir.
Dr. Moreau: I understand that I must be shocking to you, however, I must also point out that I have an allergy to the sun and that's why I put this medication on.
What are the differences between the PG-13 Version and the Director's Cut?
A
In the US, this movie starring Marlon Brando and Val Kilmer was shown in a cut PG-13 version in cinemas. This version was later also released on VHS by New Line Home Video, also with a PG-13 rating. However, they also released the completely uncut Director's Cut of the movie on both VHS, DVD and Blu-Ray. The latter runs approx. five minutes longer than the PG-13 Version. A detailed comparison between both versions with pictures can be found here.