Slight spoiler, for GRFS follows.
Playing through the campaign, on the third mission, in Nigeria. Mission briefing states that:
"... There's been a lot of activity in the Niger Delta recently. Turns out, the CIA already had an asset in country, to monitor a PMC operating in the region... Watchgate says they're providing security for oil companies, but it looks like that's not all they're up to...."
Could it be our beloved Sam Fisher operating in Nigeria? An "asset" doesn't mean someone directly connected to the CIA, but could just be someone on the ground, who is gathering intel that is making it's way to the CIA, by other means - Like Third Echelon, for example.
Post here, as you guys play, for any other *possible* Splinter Cell references, or references to other TC games. We know that the Clancy universe is well traversed, within itself. There is no doubt in my mind that we will see a link between franchises again, given the already apparent similarities between GRFS, and "Broken Arrow" (missing nuke), that was accidentally leaked, with SC6.