http://www.museumofhoaxes.com/aprilfool2.html

It is that day, y'know....

WNOR here in Norfolk VA about 10yr ago did one, We have a landfill that they made in to a park. (not kidding) MT Trashmore, Well the joke was it built up a "gas" don't remember what they called it, something fake and it was going to explode! One of the 1st calls to 911 was the VA Beach PD wondering WTF is going on poeple are freaking!
People evaced old ladys in O2 tents and should not be move and stuiff.
2 hr in to h\it they had to keep saing they where kidding. FCC did not joke around. DJ'* where off air for over a month and the station allmost lose it'* lic.

I gotta say tho, the biggest prank ever, even tho it wasn't for April Fools, or even intentional, was the "War of the Worlds" broadcast with Orson Wells....