Thats a cute, fat caterpiller you have yourself there!

I think your friend might be either the "Tomato Hornworm" (Manduca
quinquemaculata L.) , which would turn into a Five-Spotted Hawk Moth (http://en.wikipedia.org/wiki/Manduca_quinquemaculata) -- or a "Tobacco Hornworm" (Manduca sexta L.) (http://en.wikipedia.org/wiki/Tobacco_hornworm).

Heres some more strange-green caterpillars (i've always been facinated in insects!)

http://whatsthatbug.com/caterpillar_2.html (and)
http://bugguide.net/node/view/4747