Wierd green worm

[puffcrusader696]

on my goniopora (sp?) i found a green worm (same color as the coral) crawling around on it under the moonlights. looks like a bristleworm without the bristles and just green. i thought it was some sort of tenticle until i pulled it and it came right off. the coral has been doing fine so i didnt take it out. wondering if anyone has an explanation for this or knows what it is. Thanks