Anthony Hopkins deliberately provoked Jodie Foster off-camera by mocking her rendition of a West Virginia accent, which helped her convey Clarice's outrage when Hannibal taunted her for hiding her in-character accent.
And taken Up to Eleven by John Douglas, whom the character of Jack Crawford was modeled on: Scott Glenn consulted Douglas as part of research. Douglas played him tapes of a young teenager being tortured by serial killers Lawrence Bittaker and Roy Norris; Glenn left the office in tears. He refused to take the role in the sequel as a result.
When filming phonecalls, it is standard practice to film both sides separately and have the actors pretend they're having a phone call. At the end of Silence they hooked up the phone to the phone network and had Hopkins call from the set of another movie across the country. When Jodie Foster picks up the phone and Hopkins speaks back to her the look of surprise on her face is genuine.
Executive Meddling: There was not going to be Hannibal Rising, except execs told Harris someone else would write the book if he refused.
Life Imitates Art: In the book, the FBI approaches Johns Hopkins, a known center for sex-reassignment surgery, for help tracking down Buffalo Bill. The institute refuses, objecting that this would give transgender people a bad name. After this exchange was cut from the movie, real-life activist groups made the same complaint about the film.
In the book, the FBI was able to get what they needed by emphasizing that they didn't want names of people they'd approved for the surgery, but of people they'd rejected because they were not transgender. The diagnosis of Lecter's that they were going by pegged Buffalo Bill as more of a transsexual wannabe.
Throw It In: Ft-ft-ft-ft-ft-ft. Hopkins threw this in as a joke at the end of the take (hence the long pause between the end of the line and when he actually starts the noises) but the director decided it was appropriately creepy and kept it.
Silence was initially put together at the behest of Gene Hackman, who planned to direct and star as Hannibal Lecter. When he left the project, Robert Duvall was considered for the role. Dustin Hoffman, Robert De Niro, John Hurt, Christopher Lloyd, Patrick Stewart, Jack Nicholson, and Jeremy Irons are also rumored to have been in the running. Michelle Pfeiffer was Demme's original choice for Starling, and her refusal cleared the way for Jodie Foster. Mickey Rourke was offered the part of Jack Crawford and turned it down.
Other actresses considered for the role of Starling included Nicole Kidman, Halle Berry, Andie Mac Dowell, Meg Ryan, and Melanie Griffith
Michael Keaton, Mickey Rourke, and Kenneth Branagh were all considered for the role of Jack Crawford.