These introduce variations involving infidelity, illness, and tragedy.
This is a famous metafictional short story often studied in literature. It provides several different scenarios (labeled A through F) for the lives of a couple named John and Mary: The Happy Ending
While the phrase "Happy Ending" often refers to a generic story trope where "they lived happily ever after", it is also the title of several specific creative works. Depending on what you are looking for, here are the most prominent "Happy Ending" stories: These introduce variations involving infidelity