In what could be the most explosive feud since 2Pac versus Biggie (OK, it's not), the Hanson brothers are going after Justin Bieber, with the '90s teen idols comparing the pop star's music to a sexually transmitted disease. During an interview with an Australian radio station on Sunday, Isaac, Taylor, and Zac Hanson of "MMMBop" fame were challenged to a game of "Whose Song Is It Anyway?" US Weekly reports.