As the last survivor of his clan, Knuckles lived most of his life in seclusion on Angel Island, an island floating in the air; and as such he is something of a loner. His inexperience with off-islanders leaves him very honest, and also gullible. Knuckles is shy around girls. Although he is cool and determined in battle; his short temper gives rise to situations in which Knuckles, often instigated by the trickery of Dr. Eggman, begins fighting Sonic the Hedgehog.In the anime Sonic X, when Amy asks Sonic why Knuckles wouldn't come with them, Sonic replies "That's Knuckles. He does things his own way." Although he and Sonic fight from time to time, there is an undercurrent of mutual understanding between the two. Ever since the introduction of Shadow the Hedgehog as one of Sonic's darker, more anti-heroic rivals, Knuckles' relationship with Sonic has seen as much more friendly by comparison, and they both rarely fight anymore. Additionally, Knuckles has been tasked all his life as being the Guardian of the Master Emerald, as only descendants of his tribe are capable of controlling it. If Sonic exemplifies the wind, then Knuckles is the mountain: stern and anchored to his duty. However he finds Sonic's adventurous lifestyle enviable. Various literature from the early games list his favorite food as being fruit, or to be more specific, grapes. He also is described as hating strong light; in Casino Park in Sonic Heroes, if you keep the characters still for long enough he'll say, "Everything is so twinkling and bright. I hate it!!"

(Source: Wikipedia)