I found this monster who could have been the inspiration for the beast in Alien, a perfectly matched green to the plant, about 2.5 inches long, multiple legged, with a rounded face that reminded me of Flipper, happily devouring leaves and stems. Have a pix, if it can be attached.
If you can post the image on the web (perhaps somewhere like flickr?) then include the address in your question then we can all take a look! Alternatively, maybe you can find the little bugger on BugGuide.net