Well, as you know, I wrote a LND fanfic (although not a happy-ending one) in which the big twist is the identity of Gustave's little sister as the unknown female to whom Raoul is so inexplicably devoted ;-)
And I thought I was being terribly original at the time...

The "unfinished Romantic Idiots" is the story I pinched the plot twist about Erik's sexual ineptitude from for the purposes of "All the Rules Rearranged", right? ;-D