Creepy crawly on my jacket

I'm never quite sure what these tiny, green caterpillars are. I happened to notice this one crawling on my black jacket that I had taken off earlier and placed on the passenger seat of my car. I pulled over on a gravel backroad so that I could let this little caterpillar out, but of course I had to take a few photos of it, too. Taken on 24 August 2013. Not sure where I picked up this little hitch-hiker, but I had been at Forgetmenot Pond, Kananaskis, earlier.