The Unfortunate Event
Also known as The Unhappy Event.
When reviewing the film Harry Potter and the Half-Blood Prince, in order not to provide a spoiler into one of the major plot points of the film, it was referred to as The Unfortunate Event. This was because the week before, while "nurdling" (ie filling in some time before a race from Newmarket), Simon had massively revealed the end of the book, resulting in much listener anguish (though Simon insisted that there would not be a single person seeing the film who did not already know what was going to happen).
Henceforth, other similar situations where a major character dies unexpectedly have been referred to as this.
Even up to the release of HP7A, the Good Doctors continued to try to avoid revealing the precise nature of the Unfortunate Event - until they played the clip, which happened to involve the three central characters discussing Dumbledore's will.