Regular-Irregular is the first studio album by South Korean boy band NCT 127, the second sub-unit of the South Korean boy band NCT. Described as a multi-genre concept album with a total of eleven tracks, the album was released by SM Entertainment on October 12, 2018, and distributed by IRIVER. This marks NCT 127's first Korean major release in a year and four months since their previous EP, Cherry Bomb, which was released in June 2017. It is also their first release as a ten-member group since the addition of Jungwoo in September 2018. Upon its release, Regular-Irregular attained commercial success in both South Korea and other countries. The album debuted atop the Gaon Album Chart and became one of the few releases to stay longer than a single week at No. 1 in 2018. Additionally, it debuted at No. 86 on the US Billboard 200 in the week of October 27, 2018, thus becoming NCT 127's first entry on the chart. It is also the group's highest charting release on the UK and France's download albums charts and first entry on the Australian Digital Albums chart. On November 13, 2018, NCT 127 announced the release of the album's repackage, Regulate with teasers of the members. The album and its lead single, "Simon Says", released on November 23, 2018.The album's repackage, Regulate, was released on November 23, 2018, along with its lead single, "Simon Says". NCT 127´s single “Simon Says” from the repackage album “Regulate” written & produced by Dsign Music and Bobii Lewis from EKKO Music Rights Europe was NCT 127´s first Billboard #1. After scoring their first-ever Billboard 200 album entry in October with Regular-Irregular, NCT 127 earn their next chart accomplishment with new single “Simon Says.” The boy band’s electro/hip-hop/pop hybrid single debuts at No. 1 on Billboard‘s World Digital Song Sales chart giving the group their first chart-topper on the list. “Simon Says” sold 2,000 copies and logged 2.1 million on-demand U.S. streams (audio and video combined), according to Nielsen Music, for the week ending Nov. 30. It marks one of the band’s best sales week for a single, but the result does not surpass “Regular” which sold 3,000 copies when it debuted at No. 2 on World Digital Song Sales in October.