In one episode, Homer and Marge conceived Bart in 1980 after watching The Empire Strikes Back at the cinema. Later on however, Bart and his younger sister Lisa were unfamiliar with 1990s culture.

Being a beautiful boy, Bart is a self-proclaimed underachiever and prankster who is constantly in detention, and, in addition to his behavior, is easily distracted. He is the most misunderstood of the family (after Maggie, who currently can only speak a few words), constantly frustrated by the narrow-minded people of Springfield, who judge him merely by his thoughts and actions.

His penchant for shocking people began before he was born, Bart "mooned" Dr. Hibbert while he performed a sonogram on Marge when she was pregnant with him, and moments after being born, he set Homer's tie-on fire, starting his life as a prankster (although Marge claimed that he could not have done it on purpose because he was only ten minutes old). Bart's first words were "Ay Caramba" after he walked in on Homer and Marge at a bad time.

When Lisa was born, Bart got jealous of all the attention Lisa was getting sick and tried to make himself the center of attention. Bart eventually couldn’t take …

―Bart

Bart is a kindhearted, loyal and energetic, but sometimes very rowdy and mischievous boy.

Bart is a notorious prankster at Springfield Elementary, and his pranks are often elaborately complex, but can lead to unfortunate consequences. Bart's overall intelligence, like his mother's, has been shown to fluctuate slightly over the course of the series. It has been shown anywhere from being just above his father's level, to being just below, or (on the rare occasion that he shows interest or is willing to pay attention) exceeding that of his sister. Despite his behavior, Bart is also extremely good at science, art and even sports like skateboarding. His actions and speech frequently show considerable mental agility, street-smarts, and understanding. When Bart became a hall monitor for Springfield Elementary, his grades went up, showing that he only struggles because he does not pay any attention. Bart has ADHD. This has been exaggerated to the point he is willing to do Algebra, so long as it is a distraction from his actual homework.

On the other hand, Bart often seems to have trouble understanding even the …

Bart has had many relationships with girls and in the future marries and divorces Jenda. However, he has also been hinted as being attracted to boys. In "Bart’s Friend Falls in Love", Milhouse is smitten with a transfer student named Samantha Stankey; Bart schemes not to steal the girl but to detonate the affair so he can have Milhouse back. Whatever discomfort Bart evinces at Milhouse’s emotional attachment to him takes the familiar, unsubtle form of denial. And when Bart does find friendship with another boy, it’s expressly coded as romantic: "The Haw-Hawed Couple" of season 18 sees him growing close to class bully Nelson Muntz, only to wind up fearing the intensity of his devotion. In the end, Bart wistfully cradles one of his denim vests — an allusion to Brokeback Mountain.

So it can either be down to Bart being possibly drawn to both genders or his emotionally sensitive side leads him to acting more emotionally closer with others in some circumstances, regardless of who.