When Lionel and Joyce speak to the lawyer regarding Jeffrey's brain, they show a shot of it in a jar. The Preservation Date is 11/31/1994. There are only 30 days in the month of November. Later, when the brain is in a box about to be destroyed, the date on the box has been corrected to 11/30/1994.
Christopher Scarver did not kill Jeffrey Dahmer after Jesse Anderson. He killed him first, and he did not, as this episode shows, give him a "furious vengeance" style sermon like in Pulp Fiction (1994). He killed Dahmer quickly before killing Anderson, not knowing how much time he'd have to do so.
Right before John Wayne Gacy's execution, he's asked if he has any last words. While he looks at the witnesses of his execution, he says, "How about you all kiss my ass?" According to prosecutor William Kunkle, the words "kiss my ass" weren't part of Gacy's official statement prior to his execution. He allegedly said those words to a prison official.