Actor Im Chang-jung's worst nightmare came true when he returned to the musical stage for the first time in 10 years: He forgot his lines.

Im, who played the role of Daniel in the musical "Mrs. Doubtfire," called it the "mistake of his life" over and over again during an interview with reporters on Thursday.

“I’d never made that kind of mistake in my life. Forgetting an entire line of a scene. I felt terribly sorry for the audience and still think about how I will pay them back,” Im said, his regret and distress at having let down the audience and fellow actors apparent.

Even though his last appearance in a musical was a decade ago, when casting for the musical adaptation of “Mrs. Doubtfire,” Im, a versatile singer and actor who is known for his wit, was considered the best match for the main protagonist Daniel. Played by Robin Williams in the original movie, Daniel is a struggling, out-of-work voice actor, who is also a devoted father.

Im remembers accepting the offer without too much forethought because it just made sense at the time, but little had he known that the project would be a huge challenge.

The quick change between Daniel and alter ego Mrs. Doubtfire brings catharsis to audiences, but the intense dancing, singing and acting to prep for the nearly three-hour show led him to lose 7 kilograms since the musical opened Aug. 30.

The 48-year-old, who made his acting debut in 1990, was familiar with being a solo singer or playing a lead role in movies. When he made mistakes during his concerts, he admitted that they largely went unnoticed as he was able to skillfully manage the situation.

He confessed he’s long been the type of person who thought he was the only who had to do well. He said he was arrogant and pushed his ideas without paying much attention to other people’s opinions. “Without realizing that I’m wearing a sword, I would just move around and accidentally cut other people,” he added.

But a musical setting is entirely different -- time is of the essence and he has to be in sync with other actors and staff -- and that new environment put a lot of pressure on him.

"If I missed a line, that has a huge impact on the fellow actors and interrupts the feelings of the audience following the story," Im said. "I've realized I'm part of a cogwheel and I have to do a better job," he said, adding that he would put in his utmost effort until the very last performance.

He has learned a lot from his fellow actors with whom he shares the role of Daniel -- played by comedian-turned-actor Jung Sung-hwa and musical actor Yang Joon-mo. He watched them perform the role onstage at least six times.

“I learned brilliant ad-lib skills from Jung Sung-hwa and the way he makes the voice of the granny and the way Yang Joon-mo portrayed Daniel as a responsible father, which was different from my perception of the character as an immature father. I think Yang’s approach is great,” Im said.

The story of Mrs. Doubtfire resonates with his life, he said, having been divorced once. Im, a father of five sons, said he was able to empathize well with the character.

“I cried when I was rehearsing the last scene, but onstage, I’m so nervous that I can’t even cry,” he said.

In the last scene, Mrs. Doubtfire, who became a TV host, responds to a letter from a girl who is worried about losing her family after her parents' divorce.

“Just because they don't love each other anymore, doesn't mean that they don't love you. There are all sorts of different families, Katie. ... But if there's love, dear ... those are the ties that bind, and you'll have a family in your heart, forever.”

Im said he believes in the musical's powerful story and that the production team has been working very hard on the show.

"So if I can be a bit greedy, I hope 'Mrs. Doubtfire' can win a musical of the year award," Im said.

“Mrs. Doubtfire,” which runs until Nov. 6 at Charlotte Theater in Seoul, is being staged outside the US for the first time.

(gypark@heraldcorp.com)