There are several unreleased tracks produced by twenty one pilots.
Three demos surfaced on the internet. One of which (produced in 2013) has been rumored to become "Doubt" or "Hometown". Another one (produced in 2011) hasn't proved to sound like any song currently released. The last has a title, "Korea" and came off of the Regional At Best webseries video Korea: 2012.
Only two songs have known alternate versions not released on an album. The first being "Air Catcher" which the original appeared on the 2009 self-titled release. The second, "Screen" is rumored to be a demo version made during the Regional At Best era.
A 32 second song clip only known as "I Need Something" surfaced in 2012 which was made back in the Regional At Best era.