On October 30, 1938 — okay, the day before Halloween — Orson Welles broadcast to the US his rather creative version of H.G. Wells' War of the Worlds. As most of you likely know, after starting his regular radio program with a sententious (and somewhat boring) reading of the first part of the 1898 novel, Welles's Mercury Theater on the Air players interrupted with a series of mock news reports that eventually told of an invasion from Mars. Panic ensued in many parts of America. Gotcha!
Thanks to the miracle of the internet, you can listen to the hour-long broadcast online or download it for later. It's really rather well done. The interruptions build the tension, and the use of generic dance music as filler presents a lovely contrast. Canadians might want to take special note of the report occurring at the 9:40 point, where from "Toronto, Canada, Professor Morse of McMillan University…" notes a series of explosions on the red planet.
The Wells novel has been filmed more than once, of course — and, indeed, has been turned into a musical, of all things. I vividly remember seeing the 1953 movie as a kid and being thrilled. What I didn't notice at the time is that in one scene, as the reports of disaster start coming in to the assembled generals, one of them reads a note and tells the others, "Montreal's blacked out. Nothing more's come through." (You can treat yourself to this at the 0:54 point in the movie trailer.) It must be that there's something about Canada that lends verisimilitude to American works, at least where wars of worlds are concerned.
And the radio hoax thing has been done more than once, too, importantly only a few years before the Orson Welles program. In 1926, Ronald Knox, a priest, broadcaster, and mystery novelist, interrupted a regular radio program to inform listeners that workers were rioting in London. In that case, too, there was dance music interspersed with ever more feverish reports of advancing destruction — the clock tower in which Big Ben hangs toppled by mortar fire, the Savoy Hotel torched… It seems likely to me, at least, that this was the very model that Welles used in planning his joke. There's a nice touch of irony here, too, (though, oddly, no mention of Canada), in that newspaper reports in the US at the time boasted that such a panic could never happen in America because, unlike the UK, no one broadcaster in the US had a monopoly on the news. The panic that followed Welles's broadcast a dozen years later was much more serious than anything that occurred in Britain after the Knox joke.
[PS Note the location of the apostrophe in April Fool's. Wikipedia would have me put it after the 's'. But the OED plants it firmly after the 'l', letting us know that it's the universal fool, the Everyfool, we're talking about here, mon semblable,—mon frère!]