A Man Who Was Superman

SONG Soo-jung is a producer going on her third year at a small company. Her specialty is human interest stories. She is driven to produce these shallow stories for the sake of her ambition of one day becoming Koreas own Oprah Winfrey. However, she is reaching the end of whats left of her pride. One day, after months of not getting paid, she leaves her office with the company camera to produce a story on a lion apparently refusing to eat its meal. On her way, however, she comes across a robber, but she is saved somehow by Superman in a Hawaiian shirt. Superman claims hes unable to tap into his supernatural powers as the bad guys have placed kryptonite inside his head. However, he doesnt let that get in his way from helping others, from saving the world from global warming to saving a lost puppy. Soo-jung can see this will make a good story and, with a little tweaking and a little fabricating, she produces the Superman Saves the World documentary which goes on to be a ratings hit. However, the true story behind this Superman, including the bullet and not the kryptonite that is lodged in his brain, helps the frosty, calculating Soo-jung to awaken to whats truly important in life.Soo-jung is a cynical and worn out producer of television documentaries. One day, after months of not being paid, she leaves with her company's camera to shoot lions in Africa. But before she gets the chance a thief tries to steal her camera, only for her to be rescued by a man in a Hawaiian shirt who claims to be Superman. The man (whose real name is later revealed as Lee Hyun-Suk), who spends his days trying to help others, believes that a piece of kryptonite lodged in his brain has robbed him of his powers. Soo-jung decides to make him the subject of her new documentary. After an X-Ray, it becomes clear that there really is something stuck in his head: a bullet. Over the course of the movie, Superman's story is revealed. Two past tragedies that befell Hyun-Suk has led him into the current state of mind he is in. When he was a boy, he saw Superman with his father, who told him that if he counted to one-hundred, he would become Superman. His father later died in a gunfight, and the boy was hit in the back of the head with the bullet, miraculously, he lived. Years later, he and his wife and daughter were caught in a car accident. His wife died instantly, but his daughter was still alive. The man told his daughter to count to one hundred, and he'd turn into Superman to save her. Unfortunately, just as he was running to the car with a fire extinguisher, the bullet caused a seizure, and as he lay on the ground in pain, the car exploded. Nobody in the crowd tried to help. This was when he became Superman. As the story goes on the car explosion repeats again as a police officer is stuck under the car and a child in the burning building. Then he goes to the rescue, with all his hope lost, people started to help. He saved the man with others but the child alone. In the burning building he couldn't escape so he jumped out the window. From there he flew and went back to the past to save himself from the bullet which now goes in to the future where he landed on his head saving the child. In the hospital there was an S when they were about to take his organ. Soo-jung then did what the man did in the beginning of the movie helping out an old lady. A phrase used by Superman earlier in the film is reiterated by Soo-jung "Strength doesn't open big iron doors but a small key" which then leads to the credits. [D-Man2010]

Question: What phrase does Lee Hyun-Suk say in the hospital?
Answer: Strength doesn't open big iron doors but a small key