Obito Uchiha

appears in the Kakashi Gaiden arc as a former teammate of Kakashi Hatake and a member of Team Minato.

Background
Obito graduated from the Ninja Academy at the age of 9, and got promoted to Chunin at the age of 11. During the Third Great Shinobi World War, Team Minato is assigned to destroy the Kannabi Bridge. Because Kakashi has recently been promoted to Jonin, he is to be left in charge of the mission. Before setting out, however, Minato Namikaze and Rin give Kakashi gifts, something Obito forgot to do. Minato leaves them to go fight on the front lines, and Rin is soon captured by Iwagakure forces. Kakashi chose not to go save her, placing the mission's completion first, but Obito refuses to comply, stating that while those who break the rules are trash, those who abandon their friends are worse than trash. They part ways.

When Obito finds where Rin is being held, he is immediately attacked by Taiseki. Kakashi, having had a change of heart, arrives in time to save Obito and Taiseki uses the Hiding Camouflage Technique to disappear. Invisible, Taiseki is able to damage Kakashi's left eye. To save his teammate Obito awakens his Sharingan, immediately proving proficient enough with it to locate and kill Taiseki. Obito and Kakashi go to save Rin, but once she is freed an enemy-induced cave-in starts. Obito pushes Kakashi out of the way of a falling rock and his right side is crushed. Unable to free himself, Obito asks Rin to give Kakashi his remaining Sharingan eye to make up for not giving him a gift earlier. Once the eye transfer procedure is complete Rin and Kakashi are forced to leave, the cave continuing to collapse around them. Obito is then crushed by boulders as he is thinking about his two teamates.

Personality
Obito was constantly tardy, always claiming he was doing a good deed--such as helping an elderly woman carry her luggage. Minato refers to this as the truth though Kakashi doesn't believe him. Obito was also a little stubborn at times, yet unlike Kakashi who was very strict of the rules and regulations, he was usually carefree and would rather save a teammate than complete a mission--the same way of how Kakashi's father, Sakumo Hatake. Obito would also lie to get out of trouble or just an uncomfortable situation--whenever he would start crying, he would claim he had something in his eye, though usually at the time he had his goggles on. Obito had romantic feelings for his female teammate Rin, though he never revealed it to her, not even when he was dying.

Obito looks similar to Naruto Uzumaki, and they both also have similar personalities. Both Naruto and Obito were desperate to get attention as a child, they both have an epic rivalry with their other male teammate (Sasuke and Kakashi), and they both have romantic feelings toward their female teammate (Sakura and Rin). Also, their partners have similar personalities: both Rin and Sakura are Medical Ninja, and both of their loves are more prominent than Obito's and Naruto's. Also, both Kakashi and Sasuke were the top students at the Ninja Academy, and they're both considered "cool" by most of the other students. Obito and Naruto were considered "goofballs" or "knuckleheads" because of their recklessness.

Trivia

 * Although he has yet to make an actual appearance in the anime, he is seen in a picture twice. The first time his goggles are colorless, and the second time they have a faint orange-tint like they do in color illustrations from the manga.
 * Before Tobi was revealed to be Madara Uchiha, several fans hypothesized that he was Obito Uchiha, as his only shown eye was the opposite of the eye that was inserted in Kakashi. They also have similar personalities, hair styles, as well as the same blood type, "O". The spelling of Obito was also similar to Tobi, creating the fan reference of ObiTobi, or Tobito. Even though Tobi has been referred to as Madara several times in the series, some fans still insist that Obito is somehow connected to Tobi or Madara.
 * He and Izuna Uchiha both died in battle, gave their Sharingan to another person and have the same birthday.