Haha, it figures. As soon as I posted that I thought to add 'icculus' to my search and found this on Ryan C. Gordon's site:
Notes on achievements:
So it annoyed me that we don't get the Steam Achievements for Aquaria,
so I added in a rough equivalent. This doesn't change a great deal, it
doesn't go on any permanent record (beyond $HOME/.Aquaria, I mean)...it
just gives you bragging rights. It's also, I've found, a good way to
know you really did squeeze every bit of content out of the game; you
can beat Aquaria and only unlock around 8 of the 27 achievements...you
might find there's a whole lot of game you just never saw.
The list of achievements and their descriptions (which contain minor
spoilers, btw!), are at the bottom of the help screen (press 'H' or the
question mark icon in the menu to bring it up). It'll tell you which you
achieved and which are still locked. You'll get a notification when you
unlock a new achievement, too.
For those already progressing through the game: about half of the
achievements will unlock immediately when you load your save game, if
you've already accomplished them. Some examples are "Explorer," "Passed
Through," "Romance," and "Divorce."
The following achievements trigger as you accomplish them, so if you
already did these things, you'll have to do them again with the new
build to get the achievement to unlock. In most cases, you just have to
go back to the right area, although a few will need you to redo some feat.
A New Chapter...
Dance of the Forest Sprites
Gullet
Weird Fish
North Pole
Combo Eater
Feather-mouth
No Escape
High Dive
Monkey Flinger
