In-ho Yun

At age nine, Yeomin (played by Kim Seok) attends an elementary school as a third-grader at a village nestling deep in the mountains. Yeomin is the protector of justice in his village. Yeomin beats a macho boy who has harassed his friends. Yeomin shares his lunch box with his friend who lives lonely with his sister. Yeomin sometimes becomes a peddler of ice cream and cleans a piano lesson room in order to earn money needed to buy a pair of glasses for his mother. (seoulselection.com)

Struggling artist Min Hee-do is offered three billion won to bet his life if he loses a game against a rich old man, Kang No-sik, who is dying from a terminal illness. The game is for each man to dial a random phone number and guess if the person who answers will be male or female. Hee-do loses the bet, and after a month long brain operation wakes up to find that they have swapped bodies. (Wikipedia)