Don't know if this is the right place to ask this, but I'm wondering how they created the hole in Robert Downey Jr.'s chest so they can put the reactor there? Here is the video "Iron Man: Behind the Scenes" where you can see the actual hole; this is behind the scenes so no CG.
This was done using a prosthetic chest on his real chest (make sure to sing that to the tune of "We Want A Rock" by They Might Be Giants).
Skip to 2 minutes in for an explanation.
But to sum up: RDJ is actually sitting inside the chair you see. The chest is a sculpted prosthetic laying above him.