Alexander "Xander" Lavelle Harris was a close friend of Slayer Buffy Summers and a founding member of the Scooby Gang. Being the only one of his group of friends to not possess any supernatural abilities, Xander was usually the one who saw everything beyond the supernatural. Besides this, Xander was known to be very humorous and sarcastic, especially in the face of danger.

Xander was born to Anthony and Jessica Harris and grew up in the small California town of Sunnydale some time before the middle of January in 1981. Xander's father was a self-pitying drunk while his mother was a fragile mess; both parents were negligent and even abusive towards their son, leaving him with various insecurities. Xander's lifelong best friend was Willow Rosenberg, who secretly harboured a hopeless crush on him. The pair briefly "dated" when they were five, but broke up over a stolen Barbie. In kindergarten, Xander suffered an unknown humiliation involving Aqua man underpants. Xander and Willow developed a mutual hatred of their snobby classmate Cordelia Chase, which led them to form the "We Hate Cordelia Club", of which Xander was the treasurer. At his sixth birthday party, Xander's parents hired a clown which chased him; this traumatic incident gave him a lifelong phobia of clowns and caused him to suffer from nightmares. When Xander did not get a toy fire truck for his seventh birthday, the house next door burned down and he believed that Willow had set the fire to let him see real fire trucks. When he was seven, Xander had to take a test to see if he had a learning disability. Despite being a little slow on math and spatial relations, it was assured he wasn't "challenged". When he was sixteen, he attended Willow's bat mitzvah, where his drunken parents caused a scene.

In his sophomore year of high school, Xander met Buffy Summers on her first day at Sunnydale High and overheard her bizarre conversation with school librarian Rupert Giles regarding demons and vampires. Xander and Willow discovered that Sunnydale was situated on a Hellmouth and that Buffy was actually the Slayer, granted supernatural powers and destined to fight the forces of evil. When his other best friend, Jesse McNally, was kidnapped and turned into a vampire, Xander fought him and accidentally staked him when someone pushed Jesse into the stake Xander was holding. After stopping the Harvest together, Buffy, Xander, Willow, and Giles formed the "Scooby Gang"; a small group of people who helped Buffy fight the forces of darkness.

Xander acted mainly as a sideman alongside Buffy who always provided constant comic relief. One of his main aspects in his sophomore years was his longing attraction for Buffy which he quickly developed upon seeing her. This was put alongside when a beautiful substitute biology teacher named Miss French directed his interest into her. Ignoring Buffy and her suspicions about Miss French, Xander ended up finding out she was actually the She-Mantis, a giant insect that disguised itself as a beautiful woman to seduce, mate with and eventually eat male virgins. Buffy saved Xander before he could be raped and decapitated, and his attraction was returned to her.

His feelings took a dangerous turn when he and a gang of bullies were possessed by the spirit of a hyena, twisting his feelings to the point of obsession where he sexually assaulted her as well as committing several other exploits such as bulling students, insulting Willow and eating a live pig. Buffy and Giles eventually found a way to remove the hyena spirit from him and the other students. Embarrassed, he pretended that the experience was removed from his memory, with only Giles being aware of his memories.

Returning to his schoolboy crush, Xander showed great jealousy to any man Buffy took an interest such as her brief relationship with loner Owen Thurman and her attraction to the handsome stranger Angel[14]. His hostility towards Angel grew stronger when he learned that Angel was a vampire, albeit one with a soul. He encouraged Buffy to kill him since she was the slayer and was willing to do so when it seemed that he hurt her mother. Finding out he was framed, Xander still didn't trust Angel and was shocked to discover Buffy still liked him.

Come Prom time, Xander finally admitted his feelings to Buffy, wanting to take her as his date. Buffy did not share the same feelings and rejected him, leaving him bitterly disappointed. He then asked Willow on the rebound, but, despite her crush on him, rejected his offer as she knew his true intentions. Saddened and depressed, Xander lied on his bed and listened to country music ("the music of pain"). However, he still made it his mission to save Buffy when he was told she went off to fight the Master, despite destiny claiming she would die. Xander teamed up with Angel to look for her but was too late as the Master already drowned her. As Angel had no breath, Xander saved Buffy's life by performing CPR, allowing her to kill the Master.

In his junior year, Xander still continued to have an attraction for Buffy, but to a lesser extent, and even threatened to kill her when her new distant and emotionally crude attitude after her death experience got Willow kidnapped by vampires.