I spotted via a Google Groups forum thread posted by Pamela, a Google Maps engineer, that Google Maps had their own April Fools joke. I did not see this posted anywhere else, so I figured I make its own thread.
Pamela said she "put together a quick mashup to let you position a "trick" over someone's home." It is pretty cool, check out this link to create your own. Here are three samples over New York's Manhattan.
A Sinkhole over zipcode 10025:
An earthquake over most of NYC:
My favorite is the alien bug over Manhattan:
Why is it my favorite? Because this actually did happen on September 28, 2006. A bug got caught in the satellite lens and it appeared to spot an alien bug on Google Maps. Too funny Pamela!
Forum discussion at Google Groups.