Backflesh is a fictional American rock group that appeared in iAm Your Biggest Fan. They needed a place to practice, and decided to make Spencer their drummer so that they could use the Shays' apartment. However, Spencer proved to be a terrible drummer, and the group eventually abandoned the idea. They stole Spencer's drums and wrote him a nasty letter, telling him that he was no longer considered a band member.
At the end of the episode, they were seen on Seattle Beat, where they had to contend with Mandy, iCarly's obsessed fan who had now apparently become fixated on Backflesh instead. Mandy was showing them the cookies (with the band's faces on them) she had made, and was wearing her duck mask and quacking.
Backflesh was portrayed by the real-life band, Backhouse Mike (Composer Michael Corcoran's actual band and stage name as producer) whose music is heard in many of Dan Schneider's productions. Although the band only made one appearance on iCarly, their song was heard in Season 2 and "Ripoff" Rodney mentioned having tickets for them in iDon't Want To Fight. They also appear as the background music in several episodes, such as iParty With Victorious. Backflesh also appeared on "Chasing Zoey," the series finale of Zoey 101.
Also, in Gibby's blog, Gibby says that Backflesh used his belly as their album cover, and in the iSongs section of iCarly.com, you can listen to their song "Take Me Back".