It's rare these days for a drama not to have an idol in at least a small supporting role or appearing in a cameo. But which idols would you say has already made the most successful transition from singing to acting?

Idols who are now thought of as actors include Kim Hyun Joong, Ok Taecyeon, Chansung, Suzy Bae, IU, and Kim Jaejoong. Sometimes the transition is almost seamless but occasionally the idols face daunting criticism.

In terms of the smoothest transition, and the level of acclaim, "Three Days" star Park Yoochun probably should take top honors.

With his very first drama, "Sungkyunkwan Scandal," he earned rave reviews. And by his second drama, he was sure acting was going to work out.

"Acting is very interesting," he said. "Through Rooftop Prince I was happy to learn how interesting it could be to express the character."

But he was not sure he was a good actor, modestly saying it was just that he was expressive and knew how to cry. And that he was observant of other people's actions. But that is exactly what acting is about.

Now that he has starred in several dramas, he can be pretty confident that he had talent.

Yoon Eun Hye, who began her career as a member of the girl group V.O.X., was met with a lot of criticism after she made her debut in the 2006 film "The Legend of Seven Cutter." The way she spoke in "Coffee Prince" was criticized.

Her mannerisms in "My Fair Lady" also received scorn.

"I went through a hard time with the whole pronunciation issue," she said of her "Coffee Prince" role. "I cried a lot and wondered if I could continue acting."

Fortunately, she did not give up. "Coffee Prince" is considered a classic k-drama and one that is much loved by fans. The actress won a Baeksang Award for her role in that drama and it was the first of many.

"I never thought I was good at acting," she said in her early years. "I know I got here through luck. I know I am not that good but won't I improve if I try my best."

T.O.P. a.k.a. Choi Seung Hyun was the first member of the group BigBang to take an acting role but he liked it right away. He began with the role of the assassin Vick in "Iris," then appeared in the teenage drama "My 19." His appearance in the film "71: Into The Fire" earned him praise and positive reviews and won him awards. But that's not to say it was easy.

He found it uncomfortable to see himself onscreen but says he needs to study his performances to improve. He also had problems with action scenes.

"I'm used to making big movements with music ringing in my ears, so I found it awkward to move without the music," he said. "Unlike when I'm dancing, I was embarrassed to be acting before the staff, too. It becomes easier when I'm really focusing on the acting, but I still have trouble when I have to do it again."

The idol-turned-actor won the Rookie Award at the Asia Star Awards for his role in "Alumni" and his film "The Commitment" was a box office success.