Lee Hoo (Se7en):
His blood flows in a Royal family, but Lee Hoo doesn't know it. Not knowing that he's a prince, he works at a Chinese Restaurant as a delivery boy...delivering food in the palace. He looks at everything in a positive aspect and is an optimist by nature. Though he's in poverty (poor), he lives every day freely...but one day, something happens and it's the start of his life as a royal.
Yang Soon-Ae (Huh Lee-Jae):
Everyone in the neighborhood knows Soon-Ae as an impracticable girl. She thinks preciously of her fraternal twin. But one day, she finds out that Lee Hoo is the boy that she grew up with as a child, and they start their life's together in the palace.
Kang Doo (Lee Joon):
To become a prince, he recieved training as a mastery elite. He's a great candidate. Lee Hoo's appearance makes Lee Joon get farther away from becoming a prince. He's a perfectionist.
Park Shin-Hye (Shin Sae-Ryung):
Honor and power, Sae-Ryung grew up in a wealthy family. She has never lost first place/spot at school (meaning she's very smart)...she has skills and the looks of becoming prince's wife. She always had the ambition of becoming a royal princess. However, the prince that she has always imagined of is completely different when she see's Lee Hoo's sudden appearance. A change comes to her way.
Credit to cecilia@soompi