You might not think of actors as being naturally shy, but a few k-drama actors had to overcome a naturally reserved nature to become stars.

Kim Soo Hyun, the star of "You Who Came From The Stars" was one. One of his middle teachers was recently interviewed on the SBS "Good Morning Show" and expressed surprise that he ever chose to act.

"He used to be so quiet and innocent when he was my student," said the teacher.

Like the country bumpkin turned star, he portrayed in "Dream High," Kim Soo Hyun has worked hard to overcome the qualities he lacked as a performer.

Kim Tae Hee also lacked self-confidence and did not see herself as an actress.

"I never thought I could act in front of people because I'm so shy and reserved," she said. "I had a hard time believing I would actually be able to work as an actress.

So instead she majored in fashion design, but despaired that she did not have enough talent to make a career out of it. She became a model and eventually got the chance to act. Now she loves her job.

"I had some experiences, good and bad, that helped me to become better at what I do," said Kim Tae Hee.

In interviews, Lee Min Ho's mother has spoken about what a timid child he was. To bravely stand up and sing a song in kindergarten, the singer and actor had to practice it several times at home first. By the time the star of "The Heirs" reached middle school, however, he made more friends and now could even be described as extroverted.

When So Ji Sub, star of "The Master's Sun," was a teen he was very quiet and kept to himself. He dreamt about becoming a professional swimmer.

"I was never interested in becoming a celebrity," he said. "My life was all about swimming and hip-hop."

And although he has become bold enough to act and sing, he's still not very confident about his looks.

"I think I look too normal to be an actor," he said.

Some celebrities have enough self-confidence to perform in front of thousands at a concert but find it difficult to talk to a woman they find attractive.

That's the case with Ok Taecyeon, who last starred in "Who Are You?" He says he cannot even look at a girl he likes, which makes it hard to ask a girl out on a date. And he gets nervous when he acts with an actress he admires.

"I'm not a shy guy, but either as an actor or as a singer, I tend to become nervous if I have to work with women," he said. "It's one of my biggest regrets when I look at my acting or see myself perform."

With every new co-ed acting experience, hopefully he will be less nervous.