It seems like nearly everyone is busting out the goods for their first performance of 2010 on KBS Music Bank. Aside from the special stage with Jewelry and Rainbow, IU collaborated with a surprise guest for her single Marshmallow on the 1st. The 15-year-old singer delivered her performance with Taecyeon's lover the bouncing marshmallow as usual when Yoseob joined her on stage. With his playful character and overflowing aegyo, the BEAST blondie was an appropriate choice for the bubbly song. Although he doesn't sing with the song with IU, he does liven up the stage with his enthusiastic dancing. He even promotes his own group's song Mystery with his head roll bit @1:09. Pardon my bias, but I think Yoseob's presence made the overall performance even sweeter! However, he does have some 'splaining to do when he returns back to his dormitory. I have a feeling Doojoon won't be very pleased to discover that Yoseob two-timed him behind his back. Thanks to Kacey for the tip.