What a fun soundtrack and idea! I did enjoy how each track evolved over time with new instruments, it kept things fresh. The connection between Sophie's and Puff's themes was a nice touch as well.
One suggestion I have is some reverb/panning to place instruments in the sound stage better. To me, it sounds like the guitar stuff is far away and everything else is really close up.
EDIT: Also the cover art for the boss theme is hilarious.
Good work!
