Taeyeon, being the smartest among her friends, loves to study and has an IQ of 135.

Jessica is considered lazy (well, only Taeyeon says that). She dreams to become a famous celebrety so she can show off her perfect life to her mortal enemy, Key.

Sunny is a bubbly girl who hates Sungmin (because she thinks he's crazy) and Seohyun 'cause they always fight on who's cuter.. She was contented with her life, until her mom told her one secret that ruined everything.

Tiffany always depends on her credit cards and buys clothes whenever she's lonely. She has a crush on Jaejoong and is friends with Yunho. She always hangs out with Taeyeon, Jessica, and Sooyoung.

Hyoyeon loves dancing and is 'awarded' every year at her school as the best dancer, but things would change when this guy dubbed the Dancing Machine shoves her aside from that certain award.

Yuri is the newest girl in the school, she came 2 months late. She loves to laugh, but is shy. She is scared of dogs because she was once bitten so hard by one.

Sooyoung is just as rich as Tiffany is, but hates being too rich. She owns a bike that she never touched and spends her money on concerts and food.

Yoona is one of Sunny's close friends. Her childhood friend is Changmin, but she usually ignores him.

Seohyun is a daddy's girl and always shows 'cute' stuff to Sunny's face whenever she can. She hates cleaning, but loves messing around.

Key has a straightforward attitude. He also dreams to be a celebrity, just like Jessica, one of the reason why they are enemies (both of them are trying to impress one of the teachers who is friends with a worker of a famous entertainment company).

Leeteuk is a gentleman known for his kind attitude toward others. Even if he doesn't like the person, he still tries to be kind and polite. He is considered 'almost perfect', except for his low grades.

Sungmin, despite being as cute as a plush toy, has an evil personality reserved especially for Sunny. They were once best friends, but as time passed, they became enemies.

Eunhyuk, like Hyoyeon, loves dancing. He was a new guy at their school, but is already popular for being considered as Hyoyeon's most competitive rival yet.

Donghae's best friends aren't people, but dogs. He loves dogs and would do anything for them, but he's also loyal to his (human) friends. His hobby is to prank people -- which somehow caused him to have human friends.

Kyuhyun has a friendly and mature attitude to people he isn't close wirh, but is like a five-year-old kid to his friends. When he doesn't have anything to do, he helps Donghae with his pranks.

Jaejoong is Sooyoung's older brother. He just throws his money away as easily as a kid throwing candy wrappers anywhere they want and does anything to make his 'beloved' Tiffany happy.

Yunho always teases Tiffany for not knowing the landmarks in Seoul, but always teaches her in the end. He has a secret crush on her, but never tells her because he knows that she is head over heels

Changmin is Yoona's childhood friend. He has been by her side for years, playing video games together and eating each other's lunches, but little did Yoona know that he has already fallen in love with her.