Green Hairy Man Giving The Finger

Schneiderman said
What's the story behind this guy?

DarTT said
Exactly what I was wondering

It's just 1970's humor like the yellow smiley face. Check out this link for some more 70's stuff. It's even got a T-**** iron on of the Greenie.
http://www.crushi.com/bizarre2/page1.htm