"Rum Pum Pum Pum", the album's single, is a dance-pop song with exotic hand drums, whiplash-y snares, funky sixties' guitar riffs, and synthesized squirt. Lyrically, it expresses first love on a wisdom teeth. f(x) compare themselves to the pesky molars in another one of their typically bizarre metaphors, with lyrics like, “Attention boys! I’m a bit different / I pushed aside all the others and took my place,” and, “I will pierce through your heart’s wall and grow.” The song topped the Billboard K-Pop Hot 100 chart, marking the first number one single for the group on the Billboard Korea charts. The music shows f(x) dancing to choreography by Jillian Meyers. It features three sets: one white, sparkling set, another pink room with glossy pink borders, and red room with lights on the sides. Throughout the video, the camera focuses on choreography, and zooms in on each group member walking on the white set room with floating flowers.