What did Alfonso Cuaron put into the third Harry Potter film that foretold of events in as yet unpublished Harry Potter books?

Answer 1

Although the books have now all been published there are a few things to note:

Trelawney's Prediction:

"It will happen tonight. The Dark Lord lies alone and friendless, abandoned by his followers. His servant has been chained these twelve years. Tonight, before midnight... the servant will break free and set out to rejoin his master. The Dark Lord will rise again with his servant's aid, greater and more terrible than ever he was. Tonight... before midnight... the servant... will set out... to rejoin... his master..."

Although this was not added, but rather part of the storyline, it does show us a great deal. For instance, its proves Trelawney's (rather meagre) ability to predict certain events, and we know now that she provided the fateful prophecy which we discover 2 years after the above prediction. This prophecy rather leads the entire story. It gives reason and explanation for the movements of Voldemort, it even helps Harry to see what must be done, and more importantly, it holds the inevitable future. The above prediction leads to all that follows in the stories - for indeed, Wormtail returned and assisted Voldemort in being reborn, which then led to everything else.

Without the books published, we can perhaps see that her ability to make predictions could lead to something in the future.

2. Buckbeak

Not only do we meet Buckbeak, but the all-important Sirius makes his grand escape on the beast. This is of utmost importance, for without this event, nothing else (his death, the Order etc.) would have happened with him locked up.

Without the books published, we can perhaps see that his escape was important