Sonic the Hedgehog (ソニック・ザ・ヘッジホッグ, Sonikku za Hejjihoggu?) is a supersonic hedgehog that can run at faster than the speed of sound (hence the name Sonic) and loves adventure. He acknowledges the fact that the Earth is just as cool and blue as he is. He is 15 years old, stands at 100 centimeters (3 ft 3 in), weighs 35 kilograms (77 lbs) and was born on Christmas Island. Artist Naoto Ōshima, designer Hirokazu Yasuhara and programmer Yuji Naka are generally credited with the creation of the character, a blue-furred, blue-and-peach-skinned, green-eyed 15-year-old anthropomorphic African pygmy hedgehog, who has the ability to run faster than Mach 1 and the ability curl up into a ball, primarily to attack enemies. This is a major part of the gameplay of the series.
Sonic seems to have a holy or avatar-like position (despite, on most occasions, being unaware about his involvement in the future of the world he's saving), as many of his adventures in the series coincide with the fulfillment of ancient prophecies, specifically his involvement in echidna legends (such as:the mural on Angel Island that depicts Super Sonic fighting Eggman for the Master Emerald).
Sonic's back story shan't be revealed, at least for now, but it is certain that he developed a strong rivalry with the evil genius, Dr. Eggman, and through this met Amy Rose. He had been chased by the pink hedgehog for years since, and one day found out about their son, Sonic Junior. He kidnapped the baby, but Amy, with the help of her friends, managed to save Sonic Junior's life.
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Sonic has been described as being "like the wind", and is noted for being free-spirited and adventurous. He mainly prefers to simply be called by his name and not any fancy title; in his encounters with Princess Elise (who called him "Mr. Sonic"), Shahra the Ring Genie (who called him "Master"), and Caliburn the Sword (who called him "Knave", though Sonic was especially annoyed because Caliburn was insulting him), he insisted that they merely call him "Sonic". He enjoys relaxation, but is never one to rest in the face of injustice. He is extremely benevolent and always keeps his word except when Amy tries to get in a date with him, but he willingly puts himself at risk to help others, taking on any challenge that confronts him without hesitation, though he usually sees his role as a hero as an opportunity to have fun. However, in times of crisis, he focuses entirely on the task at hand and sees it as truly serious with no real fun involved. Sonic is shown to have a remarkable capacity to forgive, as seen in Sonic Next Gen, when he quickly forgave Silver and accepted his help in saving Elise in their third encounter, despite Silver's attempts to kill him. For some reason Sonic will not take off his shoes no matter what.
Although it is variously stated that Sonic tends to have a short temper, his profile on the 4kids Sonic X anime website states that he is super-slow to get angry.
In the American cartoons and comics, the Japanese version of Sonic Advance 3 strategy guide, Sonic Unleashed, and Sonic and the Black Knight, Sonic's favorite food is chili dogs. He displays an interest in rock music, and in the cartoon Sonic Underground was a guitarist in his own band. Some official character art and a television commercial for Sonic Adventure suggests that he has a personal hobby as a DJ. Furthermore, it is displayed in Sonic Rush for the Nintendo DS that Sonic also enjoys breakdancing as it is one of his primary ways for filling up his Rush meter. His battle moves in Sonic Battle are also based on breakdancing, as mentioned in the attack descriptions. He also breakdances in Sonic Advance 3 if he finishes a level in a short-enough time. Lastly, one of his taunts in Super Smash Bros. Brawl is him breakdancing and saying, "C'mon, step it up!" He has been credited as "the fastest thing alive" since Sonic the Hedgehog (DiC) and through Super Smash Bros. Brawl.
Ironically, Sonic likes to spend his free time relaxing somewhere.
Sonic's personality has changed very much over time. Currently, he is stated to be "pure of heart and intention" (Tails refers to Sonic while talking to Cosmo, in the Sonic X' episode "An Underground Odyssey"). Sonic Unleashed booklet states that his personality is "A juxtaposition of kindness and ferocity, as, on one hand, he does all he can to snuff out evil, but he can't look away when someone is in trouble." Sonic Unleashed also has sidequests in which Sonic the Werehog is trying to convince the Elder Gregorios in Apotos that he is Sonic the Hedgehog. To prove it, Sonic undergoes a test of speed, which involves him getting a pair of glasses for the Elder in a certain time limit; a test of courage, by protecting the Elder from minions of Dark Gaia; and a test of selflessness and kindness, which involves Sonic obtaining a book for the Elder out of kindness. He prefers to comfort people, instead of winding them up, as shown many times in Sonic X. He shows modesty various times, and prefers to humble himself, unless he is taunting someone (Like in Super Smash Bros Brawl). This is shown in Sonic and the Secret Rings where Sonic prefers not to be called "Master", and where he is referred to as the "Legendary Hedgehog" ("Me? Legendary? You've gotta be kidding! You're gonna make me blush!").
At times, Sonic seems to be somewhat overconfident in his abilities; for example, when Merlina stops him from attacking the Black Knight, he is irked and asked why she did so, positive that he could have defeated him.
Sonic is shown to believe in something greater then the life he is currently in; in Sonic and the Secret Rings, he makes a mention that the Secret Rings "might even open the gates of hell", implying that Sonic himself might believe in Heaven and Hell.
In most American media, Sonic is shown to have a liking for chili dogs, but Sonic and the Black Knight is the first video game to openly show this on-screen.