Empire indicates that trivia from J.R.R. Tolkien's "The Lord of the Rings" trilogy includes the number of guests at Bilbo's birthday party, facts about lady dwarves, the origin of Fangorn forest and Elvish family relationships. Trivia specifically about Gandalf includes his real name and his relationship to the Balrog he fights in "The Fellowship of the Ring."
Bilbo invites 144 guests to the birthday party that starts "The Fellowship of the Ring." He offends some of them by referring to the number as "one gross." Although there are no female dwarven characters in any of the books, the "Lord of the Rings" appendix makes it clear that they have beards just like the male dwarves. Tolkien created Fangorn, the forest that is home to Treebeard and the Ents, because he loved the image in Shakespeare's "Macbeth" of Birnam Wood moving and was disappointed to learn it was only words and never happened. Arwen is actually Galadriel's granddaughter, and Galadriel is Elron's mother-in-law.
Gandalf's original name was "Olórin," and his name in Elvish is "Mithrandir." The Balrog in "The Fellowship of the Ring" is actually of the same species as Galdalf as both are Maiar, which are angelic-type beings who came to Middle-Earth long before the events in the story. The Balrog is a corrupted Maia and is therefore demon-like.