Miley Cyrus made a surprise appearance and performance at the Justin Bieber concert in Madison Square Garden this week. The fans had no idea and the two performed “Overboard”. She also stopped by the David Letterman Show on Friday while she was in New York city. Miley has been busy on her latest film project LOL and filming in Detroit with co-star Demi Moore. Demi Moore plays Miley’s Mom in LOL.