Gangnam's Style, Fix-it Felix Jr., Jetpack Joyride and more on this week’s top free mobile apps

South Korean music star Psy’s popularity continues to spread, even on the top free iPhone apps list. Information search engine Wolfram Alpha’s Gangnam’s Style app has vaulted up the charts since its release last week, landing at the No. 3 spot on iPhone. In anticipation of Disney’s animated film Wreck it Ralph, the official game app for the movie Fix-it Felix Jr. has climbed its way to the No. 7 position on iPhone and No. 12 position on the top free iPad apps chart. Solar