SEE ALSO: JYJ releases BTS photos of Yoochun during 'Three Days' filming

Although Yoochun couldn't be any more serious in the drama, he knew how to not take things too seriously when the cameras weren't rolling and even joined the staff as a cameraman. He also flashed a contagious, sweet smile, lifting everyone's mood on set.

The drama's production company rep stated, "Even within Yoochun's normally tight schedule and tough filming, he is energizing the set with his humor... Thanks to Yoochun, who always gives a sweet smile, the staff and production crew are receiving strength and putting their all into filming."

Tune into 'Three Days' this Wednesday and Thursday!