Man, I just had one of those days. It makes me think of hiding, and well, of glass frogs (bet they can hide well). These little guys are not that common, but inhabit some streams in Santa Fe National Park. The most amazing thing, they’re see-through. Not totally, not all the way, but you can see their organs inside like this little guy. There are a few species in Panama, and differ on their see throughedness.
The Smithsonian Institute in Panama keeps a record of specimens. Check it out. If you go to a record with the headphones, you can even hear their call.