In 2003, Google decided to ignore April Fool's Day. But in 2002, Google explained that "the heart of Google's search technology is PigeonRank™, a system for ranking web pages developed by Google founders Larry Page and Sergey Brin at Stanford University."
"PigeonRank's success relies primarily on the superior trainability of the domestic pigeon (Columba livia) and its unique capacity to recognize objects regardless of spatial orientation. The common gray pigeon can easily distinguish among items displaying only the minutest differences, an ability that enables it to select relevant web sites from among thousands of similar pages.
By collecting flocks of pigeons in dense clusters, Google is able to process search queries at speeds superior to traditional search engines, which typically rely on birds of prey, brooding hens or slow-moving waterfowl to do their relevance rankings."
It's PigeonRank, not PageRank.
More Google April Fool's Day:
Google April Fool's Day 2000: Google MentalPlex
Google April Fool's Day 2004: Lunar Jobs
Google April Fool's Day 2005: Google Gulp
Google April Fool's Day 2006 - Take A Guess
Playing with privilege
2 hours ago