We'll begin a recap of Google's April Fool's Day pranks in reverse chronological order.
April Fool's Day 2005: Google Gulp
"At Google our mission is to organize the world's information and make it useful and accessible to our users. But any piece of information's usefulness derives, to a depressing degree, from the cognitive ability of the user who's using it. That's why we're pleased to announce Google Gulp (BETA)™ with Auto-Drink™ (LIMITED RELEASE), a line of "smart drinks" designed to maximize your surfing efficiency by making you more intelligent, and less thirsty.
Think a DNA scanner embedded in the lip of your bottle reading all 3 gigabytes of your base pair genetic data in a fraction of a second, fine-tuning your individual hormonal cocktail in real time using our patented Auto-Drink™ technology, and slamming a truckload of electrolytic neurotransmitter smart-drug stimulants past the blood-brain barrier to achieve maximum optimization of your soon-to-be-grateful cerebral cortex. Plus, it's low in carbs! And with flavors ranging from Beta Carroty to Glutamate Grape, you'll never run out of ways to quench your thirst for knowledge. "
Google April Fool's Day 2000: Google MentalPlex
Google April Fool's Day 2002: PigeonRank
Google April Fool's Day 2004: Lunar Jobs
Google April Fool's Day 2006 - Take A Guess