The trivia items below may give away important plot points.
Red says that Andy broke out in 1966. This was the same year as the landmark Miranda v. Arizona case before the Supreme Court, where it was decided a defendant must be informed of their rights (i.e. right to remain silent, right to an attorney, etc.), when put under police custody. That's why at the end of the film, when they arrest Captain Hadley (Clancy Brown), the officer is reading the Miranda rights from a piece of paper.
For the sewage tunnel sequence, Tim Robbins initially refused to immerse himself in the muddy water at the end of the pipe after a chemist tested the water and dubbed it lethal.
Frank Darabont preferred to end the film with Red searching for Andy. In fact, if he had been allowed to shoot the ending as he wanted, the closing shot would have been Red on the bus heading for the field. Darabont wanted to end on an open, ambiguous note. But Castle Rock insisted on a reunion between the two to please audiences. So instead of showing us a teary reunion, the film observes it from a distance. Darabont's response to Castle Rock's demands.
The $370,000 Andy stole from the Warden in 1966 may not seem a huge amount for 20 years incarceration but adjusted for inflation to 2010, Andy stole the equivalent of $2,599,855.25.
Red describes Andy's dream as a "shitty pipe dream". During his escape to live that dream, Andy crawls through the sewer pipe of the prison, literally a "shitty pipe".