I'm glad someone else noticed this, and I wish Colbert's writers would have written the segment, too. They had Colbert making yukky jabs that simply aren't his style, and I thought Spacey played Underwood as way too much of a straight man. Frank is a charmer and I expected him to play along a bit more, instead of being so defensive and unwavering. At the very least, they could've bonded over the fact that they both grew up in South Carolina!
I didn't expect Stamper to be alive, but since he is, I'm glad he's back. Characters come and go so quickly on this show, and he is one of the few that we have known from the beginning. It's good to have some depth. That being said, I never cared for the Stamper/Rachel storyline, so I hope they wrap it up and move on.