IU made a guest appearance on the March 23rd broadcast of MBC's "Radio Star," where she revealed the truth behind the identity of the mysterious male in her sticker photos. The photos had been circulating on various Internet board, and many of her shocked uncle fans have been speculating that the male was IU's boyfriend at the time. She explained, "He's not my boyfriend� just an oppa who I had a crush on during my middle school days. That oppa only thinks of me as a dongseng." IU then expressed her apologies to him for the photos being made public. Source: Nate1, Nate2