Lee Joon got to explore his dark side when he played the deranged barista Ryu Tae Oh in the drama "Gapdong." He was pleased when he won praise for his role but he's not done taking scary-crazy roles just yet.

To prepare for his "GapDong" role, he said he looked at videos of dangerous mentally ill patients and then tried to copy their facial expressions.

"I practiced so I could convey 'Ryu Tae Oh's feelings with my facial expressions alone," Lee said in an interview with enewsworld. "I worked hard to relax my facial muscles and to be able to use the muscles that I'm not used to using. I tried to focus on each scene. When I was practicing, I repeated the same scene over and over again until I could express the feelings."

In fact, he would like to try even darker roles. He spoke about his casting wish list when he appeared on the SBS radio show "Two O'Clock Escape Cultwo Show." He appeared on the program with actress Chun Woo Hee to promote their new film "The Guest" aka "The Piper." It's a film about a wandering musician who comes to a mountain village and barters his willingness to exterminate all their rats for treatment for his sickly son. It's based on the Pied Pipier folk story.

In that film, due to be released on July 9, he plays the son of the town's ruler. Actor Lee Sung Min, who recently appeared in the dramas "Misaeng" and "Hwajung," played the town's rule and his father.

While Lee Joon was on the radio program, an indie director called in and offered him a role in an upcoming film. Lee Joon said he would have to read the script.

It might be more attractive to him if the role was evil. When asked if any particular character he had seen fit his idea of an ideal role, he mentioned the Joker in the film "The Dark Knight." It was Heath Ledger's last role.

It might be that Lee Joon longs for a new bad guy role because his last role was playing such a nice guy. He played the devoted son and then husband in the Baeksang Award-winning series "I Heard It Through The Grapevine." The worst thing he did in that series was stand up to his corrupt father to save his marriage.

Whether he plays a good guy or a bad guy, the former MBLAQ singer will work hard.

When he wrapped up "Gap Dong," he said, "I still have a lot to learn, and I'm still lacking so I will practice more and work harder. I think it's better to improve on my weak points instead of being complacent."