Rookie (Red Velvet song)

Internationally, the group headlined the K-Pop Night Out concert during the 2017 SXSW Conference and Festivals in Austin, Texas, and made an appearance at KCON Mexico the following day.

"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.

[4] 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.

[8] 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.

[10] 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.

[11] "Rookie" was initially criticized for being unconventional and confusing but eventually gained popularity in the group's native country where the song topped various South Korean music charts and its hook was lauded as the biggest earworm of the year.

[2][12][13] Jeff Benjamin of Billboard labelled it as "a quirky, funk-driven dance track with an unforgettable earworm of a hook" while Jacques Peterson of Idolator called it "a testament to the barrier-breaking, musical diversity of the K-pop genre".

[15] However, The Star's Chester Chin commented that while the EP's lead single had an "insanely catchy arrangement and energetic delivery", he felt that it is its weakest track.