Younghee Mandlebom is a Korean girl who is Leslie's best friend. She is usually mean to Leonard Helperman. But she actually cares for him, even showing that she had a crush on him at least twice. She doesn't want anything bad to happen to Leonard and does not appreciate it when he does something dangerous, scary, or foolish.
Younghee is Leslie's best friend and Leonard's frenemy. She is in Leonard's class and, many of the other kids, she is often mean to Leonard and teased him on a recurring basis. But, most of the time she cared for him and had a crush on him.
She is similar to Helga G. Pataki from Hey Arnold! They both bully the main character but secretly have a crush on them.