Ability Over Appearance: Traditionally, guys called "Red" are redheads (this was the case in the novella). Initial casting calls had that in mind. The role is played by Morgan Freeman, who would not pick up that nickname naturally but owns the role anyway. It's explained in the film (though not in the novella), that Red's nickname comes from his name, Ellis Redding.
The mug shot shown on Red's parole paperwork is a photo of Morgan Freeman's son Alfonso. Alfonso also has a cameo at the beginning of the movie, he's the inmate who says "Fresh fish! Fresh fish today! We're reeling 'em in!" as the bus carrying Andy comes in.
He also starred as Fred Redding in the parody short The SharkTank Redemption.
Captain Hadley is a sadistic prison officer, but his actor Clancy Brown is one of the nicest guys in both the film and TV industry. He described the filming location as "a horrible monument to inhuman treatment of men by men" and stated that he had a problem acting out some of the brutal No Holds Barred Beatdowns he had to dish out to the prisoners.
In the same vein, Brown received multiple offers from former corrections officers to help him develop the character, all of which he turned down because he didn't want his performance to reflect badly on real COs.
Mark Rolston, the actor who played Boggs (a serial rapist) genuinely seemed overjoyed to be working with everyone in interviews and seems nothing like his character.
Bob Gunton, who played Warden Norton, is by all accounts a quite laid-back and chilled out guy (and for real, not in the evil or fake kind of way).
Vindicated by Cable: Back in 1994, it earned just over $28 million at the US box office; it has since enjoyed a remarkable life on cable television and home video. Ted Turner loved this movie so much, he made sure it was playing on at least one of his cable networks every weekend for about a decade (Helped by the fact that he had sold the rights to the movie cheaply to his own stations so playing it was cheap), which helped the film earn back its budget and give it the mainstream recognition it never received while in theaters. You can still find it on TBS or a similar channel, even 15 years later.
After Andy's escape, an unfortunate guard is sent into his tunnel to see where it leads, and when he sees the seqage pipe broken into, he vomits. Red hears this happen from his own cell and cracks up laughing. He's sent to solitary confinement for two weeks...where he continues laughing.
Red's feelings on the 1960s after he is paroled, as well as a panic attack in the grocery store that sends him running for a bathroom cubicle that calms him down because it reminds him of his cell.