Spy comes from South Korean boy group Super Junior and appeared on their 2012 album Sexy, Free & Single, with the song later lending its name to the repackaged Spy edition. Built around a secret-agent concept, the track plays on the group's smooth, confident image and the playful idea of watching and being watched. Short clips of its hook have circulated among K-pop fans on soundboards and social video, where the spy theme makes it an easy match for edits, reveals and undercover jokes. Its lasting appeal comes from that clear concept and the group's large, long-running fanbase.