"The Thing" in various game formats
I see they did the thing for the PCCS, but has anyone doe it for other rpg systems like gurps or d20?

I'm not an expert on all of the RPG's out there...but I don't recall any companies doing specifically "The Thing." A product like that would have required licensing, and the folks on this board are fairly encyclopedic when it comes to Thing related merchandise. I don't recall anyone on these boards ever mentioning it. I imgaine there are many "Trapped in an oupost and something is in here with us..." themes on the market. You could also work up a module using an existing system like you mentioned in yor previous post.

wrong place to put the question down, buddy. :?