On November 11, IU held a concert for her ongoing '2017 Palette Tour' at Kwangju Women's University Universiade Gymnasium.

The idol singer sang her numerous�hit tracks such as "The Red Shoes", "You & I", "Twenty-Three", "Marshmallow" and including her latest song "Palette".

During her performance for "Marshmallow", Block B member Zico appeared on the stage, surprising the audience as he sang a live duet with IU.

SEE ALSO: Zico leans back in solo 'SPOT!' concept photos

Prior to this, Zico was featured in "Marshmallow" as he collaborated with IU back in 2009.

Fans went wild upon seeing IU x Zico demonstrating their unique chemistry on stage.