Final answer:
Flashback is a common literary device used in alternate endings where the narrative goes back in time to reveal additional information or provide a twist in the plot.
Step-by-step explanation:
Flashback is a common literary device used in alternate endings. It is a plot device where the narrative goes back in time to tell a story that happened before the current events. This helps to provide additional context and information that impacts the resolution of the story. For example, in Shirley Jackson's "Charles," a possible alternate ending could involve a flashback that reveals Charles to be an imaginary character, offering a twist in the plot.