Article Photos: 'Gangnam Style' star joins Madonna onstage at MSG



South Korean Psy performs during the 2012 MTV European Music Awards show at the Festhalle in Frankfurt, central Germany, Sunday, Nov. 11, 2012. (AP Photo/Michael Probst)

South Korean Psy performs during the 2012 MTV European Music Awards show at the Festhalle in Frankfurt, central Germany, Sunday, Nov. 11, 2012. (AP Photo/Michael Probst)