Choi was initially rejected by the record label, which deemed him too "chubby" to fit the "idealistic version" of an idol. He later "went home and exercised really hard because I wanted to join YG Entertainment," losing 20 kg in 40 days. Six months later, Choi returned for another audition and was signed. Given the stage name of T.O.P. (Korean: 탑) by senior YG artist Seven, he became one of two rappers alongside G-Dragon (Kwon's stage name) in Big Bang. The two were paired with four others: Taeyang, Daesung, Seungri and Hyunseung and a documentary leading up to their debut was aired to promote them. Hyunseung was later dropped by Yang, and Big Bang made its official debut with five members. Their first studio album, "Big Bang Vol. 1 - Since 2007," received lukewarm receptions, and included T.O.P.'s first solo song "Big Boy". The group achieved mainstream success with the release of the song "Lies" (Korean: 거짓말; Revised Romanization: "Geojitmal") from the extended play "Always" (2007), which topped several charts upon its release. The singles, "Last Farewell" (Korean: 마지막 인사; rr: "Majimak Insa") from "Hot Issue" (2008) and "Day by Day" (Korean: 하루하루; rr: "Haru Haru") from "Stand Up" (2008), became chart-toppers as well. Following the release of the band's albums and singles, T.O.P. began working on his solo career. In April 2007, he was featured with fellow Big Bang members Taeyang and G-Dragon on singer Lexy's single "Super Fly" for her album "Rush". Later that summer, he appeared as an actor in Red Roc's "Hello" music video. He became the first member of Big Bang to venture into acting, starring in the KBS2 drama "I Am Sam," portraying the school's top fighter, Chae Musin. Despite wanting to use his stage name when acting, believing it reflects his professional side more, he is often billed with his real name, with his stage name included in parenthesis.