Given a reference text about a singer, tell me when they debuted, what their first release was, and what their most popular song is.
The singer Lee Ji-eun, or better known as IU, debuted on September 23, 2008 with her first extended play "Lost and Found". Her most popular song is "Good Day" from her 2010 album "Real" which was ranked number one on Billboard's "100 Greatest K-Pop Songs of the 2010s" list.