Google April Fools
It's an entire search engine
devoted entirely to April Fools. Put in a word and it pulls up every page related to April Fool's Day that contains that word. The Museum of Hoaxes seemed to figure prominently in the results for the few words that I picked at random, which I thought was cool. For a second I thought this was something that Google itself had created, but then I noticed the small disclaimer at the bottom: "This parody by Philipp Lenssen is unrelated to the real Google"
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