• We've all heard that Dumbledore knows pretty much everything that goes on at Hogwarts. He also didn't care if he lost all his acclaim except taking his face off the chocolate frog cards. Perhaps Dumbledore is using the chocolate frog cards of himself in the same way that the portraits of old headmasters spy on others. After all, look at all the times Harry and Ron have gotten chocolate frog cards with his picture on them. 
  Michael Note: That's definitely possible, but maybe it was just a humorous quote JKR added to remind us why Dumbledore is so cool.

• There is much speculation that we haven't heard the last of Professor Trelawny's prophecies. It is likely that she will make another before the series concludes, so why not book six?

• Harry and Voldemort can't duel because Fawkes's tail feather is in both wands causing the reverse spell effect. So Harry isn't going to be able to use his wand against Voldemort's wand; the power to kill him is going to have to come from somewhere else. Where or what it is, I don't know, but it can't be wand magic.

• Sir Patrick Delaney Podmore (the head of the Headless Hunt) could be related to Sturgis Podmore from the Order of the Phoenix.

• Dudley beat up a ten-year old named Mark Evans, who, coincidentally, shares a last name with Harry's mother. I dont think he will be Harry's lost brother because he's 10 (meaning Lily didnt die "that" night - which is impossible due to her protection on Harry). However, maybe Lily and Petunia had a brother?

• An interesting anagram: "persues Evans" = "Severus Snape". Could Snape have been in love with Lily? He certainly hated James; He could even have been "the source" that warned Dumbledore and the order that Voldermort was after James and Lily. --Submitted by Anka.
  Could this also have been the motive for Snape becoming a spy?
   It has been pointed out that "persues" should actually be spelt "pursues" - This makes this anagram void.

• From what was said in book five, it would be logical to assume that Harry is Sirius's heir. So not only will Harry inherit Sirius's fortune and properties, but he will be the owner of 12 Grimmauld Place, and Kreacher's master. Harry is therefore going to have to control his feelings regarding the betrayal of Sirius (from Kreacher), and will have more responsibilities.

• Percy wrote a letter for Ron which attacked Harry and Dumbledore - or so it seems! If the letter is read in another way, warnings for the group begin to appear: advice about Umbridge taking control of Hogwarts; Possible removal of Dumbledore from the Headmaster´s office; the Minister of Magic trying to portray Harry as a psychotic guy; and lots of others. Could this suggest Percy is working for the Order (undercover), and perhaps Mr. Weasley and Percy, in the need of a cover staged the fight? --

On page 861 of the American version of OoTP, Nearly-Headless Nick tells Harry, "I know nothing of the secrets of death... I believe learned wizards study the matter in the Department of Mysteries." I'm assuming that Nick is referring directly or indirectly to the veil that Sirius fell through. It's entirely reasonable for the veil to be a connection, gateway, portal, whatever, to another plane: the plane where people go when they die. The veil is possibly an experiment by such 'learned wizards' trying to contact the dead or make a connection to this other plane. In this case, as Sirius didn't die from Bellatrix's spell, but merely from crossing the one-way gateway into this other plane, then the whispering voices that Harry hears are the voices of the dead, and this leaves the 'veil' open for later contact with Sirius - assuming that if one gets close enough, he or she can actually talk with the dead.

• I believe Mr. Weasley will become the Minister of Magic. The reasons are two: Fudge will probably be thrown out of office for not telling anyone about Voldemort; Ron said (in book 5 that "they have as much chance of winning the house cup as dad becoming Minister of Magic." And when Ron jokes about something, he's usually right. Who better for Dumbledore to place at the top than Mr. Weasley?
  

• Recycling of a book 5 theory that never materialized, but could in future books:
  In the first book, Hagrid told Harry he didn't think Voldemort had enough human left in him to die. In the fourth book, Voldemort needed human blood to bring him back to life. At the end of book 4, after Harry explained what Wormtail and Voldemort did to him, Dumbledore had a 'look of triumph' in his eyes, could this possibly be because Voldemort was human-enough to die?

• On page 835 of the American verision of the OotP, Dumbledore said he protected Harry with old magic that Voldemort hated and underestimated, or in other words, Lily's lingering protection that flows in Harry's blood. Later on in the conversation, Dumbledore said the locked door in the Department of Mysteries has a force that is "more wonderful and more terrible than death." He also said that Harry has such quantities of that power and Voldemort has none. Voldemort couldn't possess Harry because "he could not bear to reside in a body so full of the force he detests." Dumbledore told Harry that he didn't need Occlumency after all because his heart had saved him. So could all of this mean that Lily's lingering protection was love? Could this type of strong love be the power in the locked room that Harry has and Voldemort doesn't? Plus, maybe Voldemort couldn't possess Harry because Harry's body was full of his mother's love. Voldemort couldn't stand to be in a body filled with motherly love. Voldemort never knew what a mother's love for her child is because his mother died when he was born. And he certainly didn't get any love from his father, who dumped him in an orphanage. Maybe 'love' is just what JKR wants us to think and she has told us all this to throw us off scent. There may be another power that Harry has that resides inside the Department of Mysteries.
  

• Could Harry be a metamorphmagus? In SS/PS JKR writes that Harry had grown back his hair over night after his Aunt Petunia had given him an awful haircut. You obviously have to concentrate on changing your appearance if you are a metamorphmagus, and Harry was concentrating very hard on his hair because he was worried about the way it looked. -
  

Book Seven Theories

• I think the outcome of book 7 is pretty well set. Voldemort will die, whether Harry goes with him or not is uncertain. Voldemort must die because if he lives on, with Harry dead, he will never die! No other person would be able to kill him due to what the prophecy said, he wouldn't even die of old age of disease because he isn't mortal anymore. He would just live on forever and eventually take over the wizarding and muggle world - No writer in their right minds would kill off the whole world!

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Possible Titles:

The only reference I can see here is to the Forbidden Forest, and although it holds many clues for future books, I do not think a future book will be based entirely round it. It may be that another "forest of shadows" will arise soon though. As to the fortress idea, I honestly can see no link to anything in the first five books.