explain xkcd:User: Aprilfoolsupdate!

Wow what? I can create my user page now! Yay!
About me: basic knowledge of html, nothing else
My signature: ^April_fools^update!(talk)
I like my signature, don’t touch it.
Leaderboard for top 50:

Aprilfoolsupdate!
Aprilfoolsupdate!
Born date	Not telling
Planet	Earth [citation needed]
Language	English
Stellar system	The solar system

Last day (Top 50)

Rank Score Pages Changes Username 1 8 2 12 RadiantRainwing 2 8 5 7 Ally 3 5 2 4 DollarStoreBa'al 4 5 2 4 Redmess 5 4 1 4 GSLikesCats307 6 4 1 4 Joshua Kronengold 7 4 2 3 Fephisto 8 3 1 2 Noam 9 3 1 2 Machina Lucis 10 3 1 2 Duralumin-here 11 3 1 2 New editor 12 2 2 2 Trimutius 13 1 1 1 FaviFake 14 1 1 1 ExplainEuge.ca 15 1 1 1 Andrea Cozzolino 16 1 1 1 Jacob Thrall 17 1 1 1 Kynde 18 1 1 1 John Hawkinson 19 1 1 1 Salsmachev 20 1 1 1 管委会篝火无法解放军“赐额“你去呢管理哦法？ 21 1 1 1 1234231587678 22 1 1 1 Angel Wedge 23 1 1 1 Runefurb 24 1 1 1 Penguin Zero 25 1 1 1 Elektrizikekswerk 26 1 1 1 Barry Margolin 27 1 1 1 Victoria 28 1 1 1 Steve Spivey 29 1 1 1 Sturmovik