One Tree Hill is known for being an ensemble show surrounding around the lives of characters Lucas, Nathan, Peyton, Haley and Brooke. In the later seasons, especially as they entered adulthood, more supporting characters were added. These characters served as love interests, children, and antagonists to the main group of five -- and even replaced Lucas and Peyton once they departed after season 6.
Not all of the new additions were met with praise, as some ended up taking the mantle as the show's new villain. Others, however, became fan-favorites who viewers wish had been in the show all along.
Millie Huxtable
Millie was introduced during the time jump at the start of season 5 as Brooke Davis's assistant. She served as one of Brooke's closest friends and eventually became a model for Clothes Over Bros and a love interest for Mouth McFadden.
Millie's character went through ups and downs during her time on the show, especially as her mental and physical health began to decline due to the pressures of her newfound modeling career. With her friends' help and support, Millie's health gradually improved and she eventually decided to step down from the modelling life to take up a position as field reporter. Her marriage to fan-favorite Mouth made her a welcome addition to the Tree Hill family, and her friendship with Brooke through the years proved her loyalty and kindness.
Chase Adams
Chase Adams wasn't introduced until season 4. He was the new kid in school and a brief love interest of Brooke's. While the two of them didn't work out for very long, he remained friends with everyone and stuck around Tree Hill for the years to come.
Chase and Brooke realized they were far better as friends, and he went on to date musician Mia and actress Alex Dupre. As mostly a supporting character, Chase served as a friend and love interest for other recurring members of the cast. His mentorship with Jamie's friend, Chuck, in the later seasons was a highlight of his story arc, and gave viewers a glimpse into a different side of Chase that wasn't just the default love interest.
Sam Walker
Sam Walker was Brooke's teenage foster daughter in season 5 of the series. Brooke and Sam's bond was a special moment in the series, and provided character growth for the adult Brooke Davis.
Despite Sam's rebellious ways and teenage snark, she and Brooke became an unlikely but great mother-daughter duo, and it was a bittersweet goodbye when she left to reunite with her biological mother. It was hard to love Sam at first given her bad decisions and attitude, but she quickly became a mini Brooke Davis, and fans couldn't help but root for her and for Brooke's journey as a mother.
Victoria Davis
Brooke's absent mother Victoria made her first appearance in season 5, giving viewers insight into the tumultuous relationship she had with her daughter.
Victoria's growth was a slow-burn, with her antagonizing Brooke most of the time she was on-screen. However, the two eventually were able to put aside most of their differences and developed a genuine understanding of each other by the series' end, giving Brooke the motherly love she always craved.
Quentin Fields
Quentin Fields was introduced in season 5 as one of Haley's students. Originally disrespectful and unkind, he slowly opened up and was able to express himself through his love for basketball.
Quentin developed a strong friendship with Haley and Nathan's son, Jamie, revealing a soft spot nobody knew he had. He was heartbreakingly killed by the same man who attacked Brooke at her store, and his funeral and Jamie's reaction to his death remains one of the saddest moments on the show.
Rachel Gatina
Rachel Gatina was a new classmate and enemy to Brooke Davis in season 3, and eventually became more of a frenemy to the other students in Tree Hill.
Rachel's arc was a complicated one: just when viewers thought she was becoming less of a villain and more of a friend to the other characters, she would go and steal Brooke's money or marry Dan Scott. Nevertheless, Rachel was a fascinating character and an incredibly interesting one, and the fight between her and Haley in season 4 is still iconic.
Quinn James
Haley's older sister Quinn served as Peyton's replacement in season 7. Coming off a divorce, she bonded with her sister and her husband and strived to become close to her nephew.
Quinn took a minute to cement her place in the heart of One Tree Hill viewers, but eventually she separated herself from the Peyton archetype and became her own person. Her relationship with Clay was simple and refreshing, and their union led to a beautiful marriage.
Clay Evans
Much like how Quinn was Peyton's replacement, Clay was Lucas's. Not only was he the newest male addition to the main cast, he was also Nathan's friend and agent, meaning he spent a lot of time in the Scott household.
Clay was a lot less broody than the older Scott brother, and he and Nathan seemed to get along a lot better than Lucas and Nate did at first. Clay's heartbreaking past and estranged relationship with his child added depth to his character, and watching him fall in love with Quinn was beautiful and non-dramatic, unlike a lot of other love stories on the show.
Jamie Scott
After being born during high school graduation, Nathan and Haley's son Jamie Scott was 5 years old by the time jump in season 5.
Jamie provided comedic relief for the remaining seasons of the show, and had the best parts of both Nathan and Haley's personalities. His relationships with his aunts and uncles filled the show with wholesome moments, like when he told Brooke that she was, "You're Brooke Penelope Davis!"
Julian Baker
Julian Baker was introduced as Peyton Sawyer's ex-boyfriend, but he quickly became known as the love of Brooke Davis's life. Despite a rocky start, the two fell in love and could never stand to be apart for long, with Brooke finally finding the man she had spent so many years searching for.
Julian was less sporty than the other men of the show, instead, showing interest in filmmaking. Even though he started his time on the show as a villain, he was regarded as a hero by the end, helping lead the charge to Nathan's rescue in Season 9.