Every year they will do boliao things, this year Gmail made this:
and they even linked it to the Grandfather paradox on Wiki, which, as expected, caused a massive(exaggerated) wiki war.
Details can be found in the revision history of the article.
I’m sure every region had their own prank, I heard Australia came out with Gday, which lets you search for stuffs one day in advance.
haha too bad I didn’t had the chance to use it.