WTF story is a modified version of the original Cave Story for the PC. It features:
-New enemies (they appear in the latter half of the game)
-New bosses (they also appear in the latter half of the game)
-New music (most of the songs in game are covers of songs from various videogames, read credits.txt for more details).
-Overall an entirely new game based on the Cave Story engine.
You can download the most current version (version 0.504) here:http://dl.dropbox.com/u/43330715/WtfStoryDemo%20v0.504.zip
WTF-story development blog - http://wtfstory.wordpress.com/
The blog updates every monday.
Also, here are some screenshots: