It's been a bad day, and coding pointless things usually cheers me up.
I mentioned when I posted the Random RPG Generator that I'd like to add an antagonist maker. This isn't quite that, but it's a random monster generator. Click the button, pick which bits you like, and ignore the rest.
Many of the creatures listed here are real organisms. I've used technical terminology, because that makes it easier - if you're intrigued - to look up the specific traits of your chosen monster. You might find some surprising, fiendish or bizarre biology to inflict on your players.
This is a draft, and I'll probably come back to it sometime. I'd like to add some kind of genre filter, and also some kind of weighting function so that people can (if they want) overcome the statistical skew towards invertebrates.