When we see Peter/Andy's empty prison cell, discovered by Seamus the wooden pirate, there is no poster next to the Star Wars figurines; however when Carter/The Warden walks in there is one, into which he throws a rock.
The pipe Andy breaks into is shown to be under pressure, when it sprays in his face, but when he gets in the pipe, the water is barely over an inch, and not flowing.
In the Shawshank Redemption segment when Andy (Peter) is escaping, he sees the Warden through the grill watching television. The TV has an antenna, but in the next shot the antenna is gone.
In the beginning, Peter says he got three Stephen King books, "Stand By Me", "Misery", and "The Shawshank Redemption". The movie Stand by Me (1986) is actually based on the King novella "The Body"; The Shawshank Redemption (1994) is based on the novella "Rita Hayworth and Shawshank Redemption". Both novellas were published together in the book "Different Seasons". Not only are there no King novels titled "Stand By Me" or "The Shawshank Redemption", but Peter could not have checked out three different books from the library.
Peter says he picked up three books from the library: "Misery", "Stand By Me", and "The Shawshank Redemption". However "The Shawshank Redemption" and "Stand By Me" are part of the same book, "Different Seasons", so Peter would have only picked up two books.
When Brian is talking to Stewie Wilkes about re-writing the novel he just wrote to bring his character back to life, he says he needs more paper so he can do so. However, as he is saying this, there is clearly a stack of blank paper sitting directly behind the typewriter.
When Andy tells Red, who he never met before, to go to Maine and get the box that he left there, the card says, "Red, do you remember the town in Mexico?" It is impossible for Andy to have left that box in Maine, during his time in prison, for he was in prison for more than 20 years, and couldn't have addressed the letter to Red before he was in prison because he never met Red. The card tells about the town in Mexico, which shouldn't have been mentioned since he never planned that trip until he was in the prison.
In the opening scene, Peter says he checked out three books by Stephen King from the library. In fact, The Body and The Shawshank Redemption appear in the same short story collection, Different Seasons.