Fun fact:
The Balrogs (Fiery Demon that Gandalf killed in the first movie (Durin's Bane was his name) are the same race (Maiar) as Gandalf, Sauron, and Sarumon)
Fun facts from movie:
But the Necromancer is only mentioned in brief in the Hobbit and it is another name for Sauron and in the Hobbit, Sauron's form was staying in Dul Guldur.
Also, in the Hobbit (The movie) Gandalf doesn't goes into Dol Guldur which is not in the book. It is another wizard called Radagast the Brown who goes into Dol Guldur and finds evidence of the Necromancer and reports his findings to the White Council. Plans by the white council to wage war on Dol Guldur are overruled by Saurumon who was head of the council.
Anyways just some fun facts that stuck out to me in the movie