RBB (Really Bad Boy)

[6][7] It was released as the lead single from its eponymous extended play on November 30, 2018, by SM Entertainment and Iriver Inc as the distributor, along with an accompanying horror-themed music video.

Upon its release, "RBB" received mixed to positive reviews from music critics who deemed it "controversial" and "unfamiliar" to the public.

[7] A day after, Red Velvet held a special V Live broadcast in which they introduced the preview of all the songs before performing a small part of the choreography for "RBB".

[10][11] The music video for "RBB" was choreographed by Janelle Ginestra, Kaycee Rice and Choi Sun-hee,[12] while being directed by director Oui Kim of GDW production team.

[14] Choreography scenes are incorporated throughout the video between different retro-inspired and horror-theme sets, with one of them referring to the 1980 film The Shining as members Irene and Yeri reprised the Grady twins image.

The "fun, creepy ascetic" video was regarded as a "B-movie schlock retrofitted to K-pop perfectionism", according to Forbes contributor Caitlin Kelley.

Writer Mike Nied of Idolator described the song as "the banger" that boasts "a fiercely danceable production" with a "sing-along chorus",[16] while Chase McMullen of The 405 chose the song as the "Track of the Day", praising it for upping "the ante on boisterous, feminist fun" from "Bad Boy", while still staying "in true Red Velvet fashion".

[17] In the same article for the video, Caitlin Kelley of Forbes remarked that "As a whole, "RBB" is like if cocktail music became anthemic pop and then soundtracked a horror movie.

It's a cacophony of sounds, rhythms, shrill ad-libs, complex harmonies, and a whole lot of brass" on the first listen, it was "unapologetically bold and loud" for a lead single that makes it "so unabashedly Red Velvet".

[20] In South Korea, writer Kim Sang-hwa of OhmyStar said the song received mixed reactions from the public but claimed that for those who follow the group and their music, this is normal for a Red Velvet release, that unpredictability is common for their title tracks and "RBB (Really Bad Boy)" is no exception.