[5] On September 17, a teaser video was released on the group's Twitter account, showcasing flashes of the words "regular", "irregular", and the new NCT 127 logo.

Later that day, SM Entertainment announced the addition of Jungwoo to the group and that NCT 127 would release its first full-length album Regular-Irregular on October 12.

[8] On October 8, NCT 127 released the music video of their new single "Regular" in English version, which marks the group's first English-language song.

[11] "Regular" is described as a high-energy hip hop track with sensual Latin vibes that incorporates Spanish lyrics.

[11] The Korean one addresses their current state as a group trying to make its way in the world, in contrast to the hopeful, goal-oriented swagger expressed in the English alternative.

While both versions focus on money, the Korean addresses the reality of their world versus the luxurious lifestyle expressed in the English.

The bonus track, "Run Back 2 U", is the full version of the demo song originally titled "Bassbot" previously performed by NCT members Johnny, Taeyong, Yuta, Ten and Jaehyun and then-SM trainee Hansol in a pre-debut video under the company's pre-debut group SM Rookies in 2015.

outdoor concert series stage on October 8, marking their U.S. television debut;[17][18] the group also appeared at the 2018 American Music Awards.

[21][22] On November 22, it was announced that member Winwin would not participate in promotions for Regulate as he was preparing for the group's Chinese activities.