A delightful story .. I tried to work out a way such a hoax could be played out today, and I'm sure there are other examples .. I figure, though, that with Google and the interwebs, either one of two things can happen: a) Nobody gets hoaxed because they figure it out rapidly, or b) everyone gets hoaxed because: hivemind.
Actually, now that I think of it, probably both conditions can occur simultaneously .. ouch. We really are a hive species.
My reasons for this are a) it is very difficult to find any pre-2005 citation for the joke, despite one supposed reference from 1975; b) the details of the story don't seem to me very plausible given what I know of comedians; and c) it's the kind of thing Penn Jillette would do.
So the story may have already played out in the modern era, if not in this case then perhaps in others: the 'Net is so full of nonsense and mis-information it would be very hard to tell. Social fragmentation of information sources likely makes it even easier today... you could argue that Birthers and the like are an example of this kind of hoax (or victims of it.)
It's a peek into the insider game of comedy. Every group has some gag, some saying that gets circulated that doesn't leave that group due to lack of context -- you had to be there type things -- or due to it being risque and taboo, like the Aristocrats. A similar thing for newspaper writers would be the Order of the Occult Hand [1], in which writers tried to slip that phrase into copy without the editors discovering it. These things are not cataloged because cataloging them would defeat the whole purpose. While the net has a lot of info, there's quite a bit of inside baseball that doesn't make it online.
Gilbert Gottfried used the joke in 2001 after a 9/11 joke backfired terribly, although the movie was apparently already in progress then, the author of the article says it was a well-known inside joke. http://observer.com/2001/10/observatory-6/
Having everything easily accessible through Google doesn't help. People just don't check the facts.
Some untruths even spread dispite the poster knowing the source isn't reliable, just because they have a vested interest in the subject. Blatant racism against gypsies an arabs spread like wildfire on Facebook in sweden this way.
It was the way the DJ and his audience were openly 'discussing' the hoax on the radio show and feedback in the evenings that I found interesting (and funny).
Suspect any gentle conspiracy like that now would have to be in a closed forum or mailing list or something.
Google would not help as people rarely hit the web to know more. If at all, current web with Twitter and Facebook in there would further ease spreading hoaxes. And we do see so many examples of that every now and then.
Actually, now that I think of it, probably both conditions can occur simultaneously .. ouch. We really are a hive species.