You can download the 12 minute podcast or read the transcript at this link: http://skeptoid.com/episodes/4367. Or, you can just be lazy and read Brian Dunning's conclusion:
When I'm looking up old stories like those reported in John Keel's chapter on the Grinning Man, I always try to find backup sources. Keel, as prolific as he was, often frustrates me for how rarely he cites sources. For example, he told the story about the two boys encountering the shiny green Grinning Man and described how he and a couple of friends interviewed them, but Keel failed to say how he learned about the event or managed to get in touch with the boys. So I was on my own if I was going to state here that these boys were real and actually did report this event. But, try as I might, I was able to find no corroborating sources at all. Every word printed about the boys and their shiny green man references John Keel's book as the original — and only — source. If Keel did learn about this event from some news report, it evaded my research.
So that brought me to the alleged UFO sightings that were taking place at the same time as Keel's apocryphal boys met the scary green Grinning Man. "New Jersey newspapers from one end of the state to the other," wrote Keel, "were filled with UFO reports during that period." So I set about to corroborate the specific sightings that Keel mentioned. Guess what I found: Nothing. Now, it's fair to say that online searchable news archives from New Jersey from 1966 are pretty slim, and it's a fact that a lot was reported that's not currently discoverable through an online text search. But there are other sources. There are UFO enthusiast groups who catalog every UFO sighting they can get their hands on. Keel was fond of citing NICAP, the National Investigations Committee on Aerial Phenomena, an enthusiast group that was active at the time of these events, and whose archives are now available online. NICAP lists no UFO sightings either that day or in the preceding weeks. I couldn't find the specific names of the witnesses given by Keel anywhere either, except in various references to Keel's books. So, unfortunately, I'm going to classify Keel's version of events as anecdotal, with no surviving evidence that they ever actually happened.
So basically you're left with a single anecdotal source (John Keel) with absolutely zero supporting evidence for anything he claimed in his book - even among the UFO community. Always be skeptical when you encounter similar urban legends. Especially when everything you find on the internet links back to a single source like this - fairly typical in the para world.
Keep in mind that John Keel also wrote the Mothman Prophecies (where Indrid Cold appears as well). His work was also the genesis of the Men in Black legend. I'm hoping by now that folks are beginning to see that all of this appears to be just a bunch of hooey written to make $$.
As I said above, another UFO icon bites the dust.
Edited by Rafterman, 19 June 2013 - 02:54 PM.