Unfinished ending to that RedApropos comic where he invited people to finish it.
 
Obviously I did not succeed in this task.
 
Basically, Twilight was going to say that books are boring now because they have a predetermined ending and Pinkie then pulls out a computer to let Twilight play some interactive fiction (text adventures). It then cuts to years later when Twilight is happily playing visual novels and then she realises that the games she’s been playing still have predetermined endings, and then sudden ending.