This one I'm assuming is a Swallowtail Butterfly Caterpillar. I may sound knowledgeable, but when I searched on Wikipedia for a caterpillar that looked like a bird dropping, that is what I found. Swallowtail sounds much nicer...
A groovy, spiky one. Imagine it's in focus.
Funny how the caterpillars stayed still for me to photograph, but were out of focus, but this bee was busy buzzing around and yet is in perfect focus....