Robin Williams and Billy Crystal were not allowed to be on the set at the same time during filming, for fear they would crack up the cast and crew, and cause major production delays.
Kate Winslet (Ophelia) learned on the day that she had to shoot the straitjacket scene that she had just been given the role of Rose in Titanic (1997).
The first full-length movie version of Hamlet ever made (using the Second Quarto (1604) text with additions from the First Folio (1623) to create an idealized "complete" Hamlet).
At four hours and two minutes, this is one of the longest Hollywood movies of all time.