This is one of my favorite Flash games ever. It's constantly inventive and surprising. And
weird in a good way. Mentioning anything would probably spoil bits of the weirdness for people who haven't played before.
Incidentally,
Windosill (by the same guy, Patrick Smith) is similar but much bigger and better. It's got references to Feed the Head in it, too. Unfortunately, it is not free and thus can not be posted in the Other Free Games forum. (Fortunately, it's cheap.)