Powerful wizard, mystical ancient, and befriender of hobbits, Gandalf is one of the most beloved characters in J.R.R. Tolkien's high fantasy literary epic The Lord of the Rings, his novel The Hobbit, and The Silmarillion. Because of his belief that the smallest of Middle-Earth's inhabitants could also be the bravest, he helped lead the Fellowship of the Ring and its Ring Bearer, Frodo Baggins, on a dangerous quest to destroy the One Ring and defeat its diabolical creator, the Dark Lord Sauron.
In Peter Jackson's exciting cinematic interpretation of the books, Gandalf is played by Sir Ian McKellen as a stately, warm, and stalwart figure of authority. In the books, he's not much taller than a hobbit, has a very sarcastic side, and is often perceived as mean. Appearances aside, there are many aspects of Gandalf that were not included in the films (including his involvement in certain key events), ten of which are presented for your richer appreciation of his character.
HE'S A CELESTIAL BEING
Much of the religious overtones of Tolkien's Lord of the Rings trilogy get left out in the films. It can be argued that there's really no place for unnecessary exposition, with the already lengthy run time of the films. But it should be noted that in the books, Gandalf is much more than a wizard; he's a Maia, an ancient spirit that existed before Middle-Earth came into being.
He was sent by the Valar, celestial immortals of great power, as their emissary/ambassador to the inhabitants of Arda (Earth). In his original form he was called Olorin, and was the right hand of Manwe the Wind-King and Varda the Star-Queen, Valar responsible for the element of air.
HE'S NOT THAT TALL (AND HE DOESN'T BUMP INTO THINGS)
From the moment we meet Gandalf in The Fellowship of the Ring, viewers can tell three things; he's warm, jocular, and tall. Not just tall by hobbit standards; he routinely seems to be the tallest person in the Fellowship once it's formed, even several inches taller than Aragorn, Boromir, and Legolas.
Tolkien had a few physical descriptors for Gandalf, mainly that he was "strong of build and broad-shouldered", but also that he was "shorter than the average man". He was bent with age by the time the Fellowship knew him, and Tolkien puts him at about 5'6". No doubt Peter Jackson wanted to convey his power through his height, and have it used for comic-relief when necessary in Hobbiton.
HE HAD TO LEARN HOW TO HAVE COMPASSION
As a member of the Ainur, a Maia like Gandalf wasn't created with compassion and empathy for the Free People of Middle-Earth. His fellow Maia like Sauron and Saruman felt that the inhabitants of Middle-Earth were beneath them, and thus should be the victims of their imperial subjugation.
Other Maia, like Radigast, simply didn't intervene for thousands of years, preferring indifference to the trials and tribulations of Dwarves, Elves, and Men. Gandalf's proximity to Queen Nienna, a Valar known as the "Lady of Mercy", prior to his coming to Middle-Earth helped him learn how to care for all its creatures and desire to help them overcome their obstacles.
HE'S WASN'T THAT PARANOID
The films would have you believe that Gandalf was increasingly paranoid by the presence of the Shadow of Sauron, acting increasingly more erratic as he felt the Dark Lord taking an interest in the One Ring and The Shire. There were many instances were Gandalf looked harried and bedraggled, an image that isn't in keeping with the book descriptions.
Gandalf was always dignified, even if his physical stature was somewhat diminished in the books. He radiated "a veiled power", usually in the eyes, and was always very certain of his responsibilities on Middle-Earth. Like literary Aragorn, he knew exactly what the stakes were, and pledged himself to the Fellowship understanding the risks they all faced.
HE WAS MUCH MEANER
The great Ian McKellan did a tremendous job bringing Gandalf to life, with his avuncular charm and radiating warmth. In the books, however, Gandalf wasn't nearly so pleasant, and was often a source of sarcasm and black humor. He wasn't as encouraging as he was in the films, and was far more of a meddler.
In the books, Gandalf spends half his time referring to those around him as "fools", potentially because as a Maia he's the most powerful out of anyone he comes in contact with, save for other Maia. It takes him time to become convinced that the Fellowship are capable of destroying the ring, and to come to see them as his friends.
HE WIELDS A RING OF POWER
Narya, one of the three rings of power given to Gandalf, Elrond, and Galadriel, is seen in the films, but its history with Gandalf isn't touched on. Unlike the fairly comely One Ring, it is an example of the finest Elven craftsmanship, forged by the Nolodorin prince Celebrimbor during the Second Age to grant its bearer the ability to stand against its corruptible influence. The Ring of Fire also prevents its bearer from aging
A beautiful silver and gold band with a ruby in the center, its seen in The Two Towers when Gandalf takes the form of Gandalf the White. It was presented to Gandalf by way of the High King of Noldor, who was responsible for creating the Last Alliance of Elves and Men.
HE STOPPED THE BLACK RIDERS AT THE FORD OF RIVENDELL
The Fellowship of the Ring found a convenient way to make Arwen a more integral part of the story than she ever was, rescuing a wounded Frodo from Weather Top and risking her life to take him to Rivendell. Stabbed by a Nazgul blade, he's losing life fast, and she races to outpace the Black Riders across the ford. When she reaches the other side, she raises her hand and commands the waters to wash the Ringwraiths away.
In the books, it wasn't Arwen's handiwork that saved Frodo at all, but the combined powers of Gandalf and Elrond that helped the hobbit to safety. Arwen wouldn't have the abilities capable of performing such a feat, but she needed to be around for more than just mooning over Aragorn relentlessly.
THE BALROG COULD HAVE KILLED HIM
When the Fellowship encounter Durin's Bane, the Balrog that dwells in the deepest recesses of the Mines of Moria, it almost means their end. Luckily, Gandalf is able to hold it off long enough for them to make it across the narrow fissure to safety. Gandalf knew he was the only being capable of tackling the Balrog's power, but not simply because in the film it was a towering beast.
In The Fellowship of the Ring, the Balrog is only a little taller than Gandalf, and a great practitioner of magic. Like Gandalf, it is a Maia, but had long ago been corrupted by Morgoth, the first Dark Lord, and turned evil. When Gandalf fights it after falling into the chasm, they were evenly matched, and Gandalf could have been easily slain, were it not for the Ring of Fire giving him stamina.
GANDALF WAS NEVER BESTED BY THE WITCH KING
The The Return of the King was an action-packed tour de force of heroic fantasy, but in some ways the film traded tense drama for melodrama and fast pacing. In the scene where Minas Tirith is falling to the Witch King's siege, we see him flying his winged mount, and we see him best Gandalf by making him look weak in battle.
In the book, he had a much more impactful battle of the wills with Gandalf the White, who demonstrated incredible strength and resolve. When Minas Tirith lies in rubble, the Witch King rides through the gates and "under the archway that no enemy ever yet had passed", encountering Gandalf and Shadowfax. Gandalf doesn't even budge when the Witch-King, no match for a Maia, tries to knock him off his horse.
HE NEVER FOUGHT SARUMAN
While the fight between Gandalf and Saruman was certainly exciting, no such battle existed in the books. In fact, Radigast was in the film much more than Saruman, and Gandalf had no reason to think that Saruman was as corrupted as he was with the use of his palantir of Orthanc to see into the future.