Was Alexander Dunning... *spoiler*

...the CIA agent with the "black glasses" in Guatemala? Joe, Marvin, and Frank ask him if he remembers them, because they remember him. And that they're the ones who cleaned up his mess in Guatemala. He doesn't deny it, but it is never actually stated that he is the "dorky little spook in a suit and tie" that Marvin and Frank remember while talking to Gabriel Singer in Mobile.

"Arguing with idiots is like trying to play chess with a pigeon..."