Ganon
Ganon (sometimes referred to as Ganondorf or Ganondorf Dragmire) is the monster which takes many forms from the Legend of Zelda series of video games by Nintendo, and the final boss in a number of them. His complete backstory, however, was not revealed until The Legend of Zelda: Ocarina of Time was released for the Nintendo 64 in 1998. The correct spelling is Ganon, as Gannon is originally a mistranslation in the booklet of the original game from the game's native Japanese, and is thus erroneous.
Character background
According to Ocarina of Time, Ganon was once a Gerudo named Ganondorf Dragmire - the sole man of his kind, only one male being born to this race of Amazons every one hundred years. He coveted the Triforce, the sacred artifact of the three Goddesses Nayru, Din, and Farore left behind after they created the land of Hyrule. Link, the hero of the game, unwittingly helps Ganondorf steal the Triforce when he acquires the Master Sword, thus unlocking the power of the Triforce. However, once Ganondorf touches the Triforce itself, it splits into three components that embed themselves in the three people destined to receive them. Ganondorf received the Triforce of Power, Link the Triforce of Courage, and Princess Zelda the Triforce of Wisdom.
With the Triforce of Power, Ganondorf was able to conquer the land of Hyrule and rule unopposed for seven years. At that point, Link, who had been held in stasis during that time, was awakened by Rauru, one of the Seven Sages, and encouraged to awaken the other six Sages (who had all been reincarnated as denizens of Hyrule) to oppose and defeat Ganondorf's rule. Once Link was able to do this, he attacked Ganondorf's stronghold for a final showdown, during which the power of the Gerudo's segment of the Triforce combined with his already insane hatred and power-lust to transform him into an immensely-powerful, porcine creature of pure evil. After his transformation and throughout the rest of the series, Ganondorf was to be known as Ganon. After an intense battle, Link and Zelda (whom Ganon had captured and used as bait to lure Link to his lair) were able to subdue the creature, long enough for the Seven Sages to combine their powers to seal him away.
Ganon found himself imprisoned in the so-called "Golden Land," a sort of parallel dimension to Hyrule itself, where it had been theorized the Triforce originated. Although able to break the Sages' seal once, he soon met defeat at the hands of the eponymous descendants of the original Link and Zelda. (These events are chronicled in the GameCube game The Legend of Zelda: The Wind Waker.)
Eventually, Ganon had subverted the entire Golden Land to his wicked rule, and the formerly lush and verdant world became a dark and decaying ruin. A curse was placed upon the land, dooming all who stumbled into this world to take on a new form, representing whatever was in their hearts when they crossed over. Those who did cross over were never heard from again. It didn't take long for the Golden Land to take on its new identity of the Dark World.
Many centuries later, a new Hyrulian child, also named Link (a long-distant descendant of the original Hero of Time), was able to prevent Agahnim, the corrupt minister to the King of Hyrule, from summoning Ganon back to Hyrule itself, but not before Princess Zelda was imprisoned in the Dark World, along with six other young women who were all descended from the Seven Sages. Link was himself trapped in the Dark World by Agahnim, shortly after the youth bested him in combat. Once there, Link found himself face-to-face with the legendary foe of ages past.
Throughout the history of Hyrule, as documented in the Legend of Zelda games, Ganon has returned numerous times to terrorize the land, but there is always a courageous boy named Link and a wise princess named Zelda ready to answer his challenge...
Appearance
Ganon first appeared in the original The Legend of Zelda game for the Famicom in 1986; the following year, the game was brought over to the American NES. In that game, Ganon first appeared sort of like a demonic blue pig, not unlike an Ogre Mage from the roleplaying game Dungeons and Dragons. During Link's actual fight with him, however, he turns invisible and randomly warps around the room throwing fireballs at the hero. Only a sword can cause him damage, and after being struck by it enough times he will turn red (and visible) and stop warping. At that point, Link must use a Silver Arrow to finish him off once and for all.
Ganon did not actually appear in 1989's Zelda II: The Adventure of Link, although the plot of the game partially involves an attempt by Ganon's followers to revive him using Link's blood. (Note that some reports claim that the final boss of the game, Link's Shadow or Dark Link, is actually Ganon in a new form. These claims are not, as far as is known, canonical.) In the American version of Zelda II, a redesigned "Game Over" screen includes a menacing silhouette of Ganon.
For Ganon's appearance as the final boss of 1991's The Legend of Zelda: A Link to the Past, Link once again had to use the combination of Master Sword and Silver Arrows to defeat him, although Ganon adopts some new tactics this time around, such as leaping into the air and crashing to the floor with such force as to knock floor tiles out from under Link.
Ganon was the hidden final boss of two games for Game Boy Color: The Legend of Zelda: Oracle of Seasons and The Legend of Zelda: Oracle of Ages. He appears in either game only after both games have been otherwise completed; it does not matter in which order. He has been revived by Twinrova, but the revival was incomplete, so Ganon does not speak, and is a dumb beast in these games.
In The Legend of Zelda: The Wind Waker, Ganon first appears as a shadowy phantom creature, but is soon enough revealed. The final battle of the game is two-fold: First, there is a giant puppet that looks like Ganon's monster form. The final battle with Ganon, an epic sword fight on top of a tower, could be considered one of the most spectacular boss fights in the Zelda series.
Ganon was also the final boss of The Legend of Zelda: Four Swords Adventures. The battle with him in this game is one of the easier Ganon battles throughout the Zelda series.
To date, these are the only Zelda games in which Ganon plays a role; he does not appear in Majora's Mask or any of the three CD-i games (which are considered out of canon anyway). A nightmare shadow of him is his only presence in Link's Awakening.
Ganon was also the main villain of 1989's Legend of Zelda cartoon, which was shown as part of The Super Mario Bros. Super Show in syndication that year. In the cartoon, Ganon was green-skinned and a wizard, not blue-skinned and a thief.
Ganondorf is also an unlockable character in Super Smash Bros. Melee, and is similar in appearance as in The Legend of Zelda: Ocarina of Time (thus consistent with Link/Young Link and Zelda/Sheik appearances). In Melee, he is referred to by his full name, Ganondorf and is a slower, more powerful clone of Captain Falcon, performing the same attacks and moves. Different artwork is used, however: the flame trails Falcon produces when he executes certain movements are orange or red, while Ganondorf's are purple, purple being a color that is often associated with Ganon in the Zelda series (see The Wind Waker and Ocarina of Time).
Captain-N the Game Master
Ganon (just like Link and Zelda) also appeared in the DiC cartoon "Captain-N the Game Master", as a secondary villain in the episode "Quest For the Potion of Power". This was something of a continuem of Ganon's appearance in the Zelda Cartoon. The episode seems to take place after the happenings of the original Zelda game (and maybe even Zelda II), during which Ganon is weakened. Through the course of the episode he becomes revived and double-crosses Mother Brain.