50PoundHead
Hessmania Forever
There may have been incidents that I am not aware of, since I have not really watched either of them in a couple of years but I do remember from 3 or 4 years ago (something like that) that they really seem to get along pretty well, which is kinda surprising but for some reason those two just seem to "click" personality wise. I really think it's because Colbert has the ability to make O'Reilly laugh, something not many people can do.
He kind of lets O'Reilly go restrained blowhard mode and gets his points in without poking the bear. I don't have that much of a problem with O'Reilly. He's not as smart as he thinks he is (and can be an utter boor), but he can be difficult to pigeonhole on a number of issues.