Grue.

The game feels a bit unfair, but it's so short and your options as a grue are so limited that it isn't hard to win; in-game hints are also available. There are several nice atmospheric touches like referring to the human NPC as "it", the description of the starting location, some customized responses, etc. And even many standard responses - e.g. the infamous "hollow voice" - seem completely at home in this setting.

I'd like to see more parser games from the author. Hopefully with some more polish - this one doesn't list beta-testers and is kind of rough.