"Rookie" was produced by American production team The Colleagues, who previously worked with western rap artists such as 2 Chainz and Gucci Mane, and Jamil 'Digi' Chammas who composed the song along with Leven Kali, Sara Forsberg, Karl Powell, Harrison Johnson, Russell Steedle, MZMC, Otha 'Vakseen' Davis III, Tay Jasper while its Korean lyrics were penned by Jo Yoon-kyung. The single was released on February 1, 2017 in conjunction with its parent mini album's release and music video.
Musically, the song is characterized as a pop-funk dance track. Tamar Herman of Billboard stated that the song "draws on Red Velvet's unconventional musicality to combine low-key sing-speaking and synth beats before blasting into the saccharine hook of a chorus" while its melody is "dominated by brassy horns and plinking synths". On the other hand, Jacques Peterson of Idolator described it as "a pure bubblegum ditty based on old-school funk and R&B". Its lyrics compare a girl's lover to a 'rookie', with the word being repeated all throughout the chorus and hook.
Promotion[]
A music video directed by Shin Hee-won was released on the same day as the single's release, featuring choreography by Ryu So-hee and Japanese dancer and choreographer Rino Nakasone who has choreographed for other S.M. Entertainment artists such as TVXQ, Girls' Generation and Shinee. The members claimed that it was their most difficult choreography at the time. The music video begins with all five Red Velvet members at a play as 'rookie' performers. After being offered some mysterious pink smoke by member Joy, a series of random and entertaining scenarios ensue where the members follow a floral-clad mascot in a 'Wonderland' while wearing various colorful outfits, such as blue and white Alice-like dresses and continue the chase as they fly around in spaceships. It ends with the members exiting the stage they first appeared in. Billboard likened the girls in the video to Alice in Wonderland's titular character, as they travel in a world that's part Candyland and part Yellow Submarine. Meanwhile, Bradley Stern of PopCrush called it "a colorful visual buffet including a flower dude, UFO adventures and fourth wall-breaking meta marionette moments" and added that it's the K-pop version of The Lion, the Witch and the Wardrobe.
The group performed the single on all of South Korea's music programs (Music Bank, Inkigayo, The Show, Show Champion, M! Countdown, Show! Music Core) in February 2017, performing the song live for the first time on Music Bank on February 3, 2017. To help promote the song overseas, Red Velvet headlined the K-Pop Night Out concert during the 2017 SXSW Conference and Festivals at The Belmont on March 17, 2017 in Austin, Texas which had over 2,500 spectators. A day later, they participated in KCON Mexico. On April 16, the group had a fan event for the album in Taipei. They flew to Malaysia the next month to hold a two-day fanmeet at the LG Concourse of Berjaya Times Square in Kuala Lumpur, where they performed and promoted the song through a mini showcase for the EP.
