Nicole "Nikki" O'Neil is a Mattel fashion doll, marketed as one of Barbie's core friends. Her character debuted in 2005 and is currently among Barbie's core friends along with Midge, Teresa, Raquelle and Summer. Nikki debuted in the Beach Fun Line and later in Fashion Fever Line. Since then, almost every Barbie doll has a "Nikki" version. She is a counterpart and little sister for Christie.