Semper Fi is an unreleased track from the writing sessions for their first full-length album KABOOM!. Brian has officially stated that the song was never completed past the initial demo phase and was abandoned late in 2009 after not having anywhere to go with it. He said that at first he liked it, but it quickly grew old as he wrote other songs he felt exemplified his style and the direction the band wanted to go in much more accurately. There is only one demo in existence and there are no plans to release it to the public. The song has never been performed live and is one of the last official recordings to include former member Laura Green on vocals.
The lyrics are not publicly known at this point in time.