"It now appears that the college humor magazine did more than print up the hoax announcement of a test retake. They actually sent a student to the lecture hall to impersonate a teaching assistant to administer a made up test. By the end, when only one or two students remained out of several who showed up (still not getting that it was a hoax apparently) the fake teaching assistant even gave out "a small cash prize." No one has been able to identify the fake teaching assistant or specifically attest to Carson being one of the last or last students still taken in by the joke. But if you step back you now have independent corroboration for a chain of events which - giving some allowance for exaggeration and imperfect memory - largely matches up with Carson's account.
The only problem of course is that the whole thing was a practical joke that the extremely earnest young Ben Carson not only fell for at the time but hasn't realized was a prank for the last 45 years. Even now Carson either doesn't seem to realize or won't cop to the fact that even if it was an innocent and honest mistake, what actually happened isn't remotely what he described. As with so many other anecdotes and examples, this latest incident reveals Carson as a sort of lifelong self-awareness Mr Magoo, with perhaps a dash of Chauncey Gardner, walking through life often with little awareness of what is going on around him but consistently interpreting things in the most self-glorifying and parablistic terms possible." Josh Marshall - Talking Points Memo