Aliens: Isn't It Ironic
The irony challenged have tended to get hysterical about Krugman's famous suggestion that the economy could be healed by a fake Alien invasion. He explains the context (a riff on an similarly ironic commentary of Keynes) once again here.
DeLong finds Cochrane being irony challenged (or as Krugman puts it, perhaps uncharitably, "remarkably dense").
It's unlikely to help though. The problem with the ironically challenged seems to be that they really don't - and can't - get it. Which is another reason why irony ought to be used a bit sparingly.