IU recently teased her fans with a photo from her upcoming comeback album, and now there's even more excitement to look forward to. It has been revealed that MBLAQ's Thunder will rap for a track on IU's upcoming album titled "Merry Christmas in Advance". This song is produced by Shinsadong Tiger, and it is a love song with a Christmas atmosphere. IU had made an appearance on MBC's 'Idol Army' Season 5 back in February, and her close friendship with Thunder captured the attention of many fans. The fans have commented, 'I'm curious about IU's mature image', 'Fancy composer and a fancy rapper', 'I'm looking forward to what kind of music  IU and Thunder make', and 'I hope the song will be a hit'. On the other hand, IU's third mini-album "REAL" will be released on December 9th. In case you haven't seen a collaboration between these two old friends before, check one out from 2009: http://www.youtube.com/watch?v=Zdb6ZtjFhWI Source: Starnews via Nate