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.
This is referenced in the film when Andy asks him why he's called Red. The reply "maybe because I'm Irish" is a reference to the Red character in the original novel, who was both red headed and Irish.
For that matter, Tim Robbins as Andy qualifies. In the novella Red describes him as a "small, neat little man". Tim Robbins is 6'5", but he nails the role.
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 Bogs (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).
Real-Life Relative: The mugshots of a young-looking Red that are attached to his parole papers are actually pictures of Morgan Freeman's younger son, Alfonso Freeman. Alfonso also cameos as the con who shouts "Fresh fish! Fresh fish today! We're reeling 'em in!"
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. It's also available on Netflix.
A sequence where the convicts find Jake (Brooks's pet crow) dead in a field sometime after Brooks has left the prison, and the convicts give Jake a funeral and burial. This deletion ends up providing a subtle thematic shift; as scripted, both Brooks and Jake represent the dangers of institutionalization, but as depicted on screen, Jake ends up foreshadowing Andy's successful escape in the climax of the film.
Tommy's young wife visiting him, their conversations providing a more vivid illustration into why Tommy decides to turn his life around and approaches Andy to work on getting his GED.
After Andy's escape, an unfortunate guard is sent into his tunnel to see where it leads, and when he sees the sewage pipe broken into and smells the overwhelming odor of shit, he vomits - loudly. 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, thus learning for himself what Andy (in the aftermath of the loudspeaker incident) had meant about "easy time" in the hole.
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 - thus making his choice to find the tree and rock wall more meaningful, because it runs counter to Brooks's choice.
Unusually the voiceover narration was recorded before filming began and was then played on set to dictate the rhythm of each scene. The guide track was recorded in an Iowa recording studio by Morgan Freeman in only 40 minutes. Unfortunately, there was a minor hiss to the track which sound engineers in Los Angeles were unable to eradicate. Consequently it had to be re-recorded in a proper studio; this time it took 3 weeks.
Director Frank Darabont had to change the title from Rita Hayworth and the Shawshank Redemption to just The Shawshank Redemption because several actresses sent in their resumes in for consideration thinking it was a Rita Hayworth movie. Accorting to Darabont, a supermodel's agent called him and said that it was the best script he'd ever read and his client would be perfect for the part of "Rita Hayworth"—immediately revealing just how much attention the agent had paid to the actual script.