Each Patronus is unique

[eggplant107]

No: HPFGUIDX 163876

"swapnil_d2727" <swapnil_d2727 at ...> wrote:

> I think as JK says it changes its shape due
> to attack or some sorrow resting in your mind 
> which Tonks certainly had

True, but Harry had even more sorrow. I think JKR wanted to introduce
us to the fact that a Patronus can change to set us up for the next
book. I think Harry's Patronus will change from a Stag to a Phoenix; I
think JKR will do this so that when Harry dies at the end of the book
readers can, if they wish, have a little ambiguity over Harry's fate;
rather like Frodo at the end of Lord of the Rings. 

Eggplant