List of all 4chan April 1 events.

2004 - moot pretends he's from Mexico.
2005 - moot creates a /fur/ furry board (later deletes it).
2006 - /b/'s formatting and CSS got fucked up.
2007 - Techno music played in the background of /b/.
2008 - Clippy was added to 4chan.
2009 - Text font on /b/ was changed to Comic Sans.
2010 - 4chan 2.0 was introduced temporarily.
2011 - ??? ( I don't know what happened this year ).
2012 - /pol/'s CSS was changed to a communist theme.
2013 - [s4s] board was created as the joke and it still exists today.
2014 - CAPTCHAS were in Japanese and you had to scroll to view the real CAPTCHA in order to make a post.
2015 - Clippy was added to 4chan again.
2016 - The Google+ thing where everybody had a randomly generated name instead of Anonymous.
2017 - The Board Merger. (As suggested by /qa/).
2018 - The Easter Porn Princesses.
2019 - A like system is added to posts. You can "like" posts.
2020 - I think this was the virus quarantine one.
2021 - Day of the rake.
2022 - Emojis are added.
2023 - Chat GPT4chan.
2024 - The Yotsuba meme Stock Exchange.
2025 - ...