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 7 days (Top 50)

Rank Score Pages Changes Username 1 25 18 30 FaviFake 2 21 17 21 TheusafBOT 3 14 9 16 DollarStoreBa'al 4 11 11 11 Victoria 5 7 4 7 BunsenH 6 6 3 6 DKMell 7 5 2 5 Jacob Thrall 8 5 1 5 Lychee Fox 9 5 5 5 August Fuller 10 5 2 4 Kynde 11 5 2 4 Chronotix 12 4 2 3 Gardener 13 4 2 3 Utdtutyabthsc 14 4 1 3 Logalex8369 15 3 1 2 Barry Margolin 16 3 1 2 Velocifyer 17 3 1 2 Christian 18 2 2 2 The Shard Insanity 19 2 2 2 J-beda 20 2 2 2 SlimothyJ 21 1 1 1 GammaRaul 22 1 1 1 Chadliness 23 1 1 1 管委会篝火无法解放军“赐额“你去呢管理哦法？ 24 1 1 1 Michael Thomas Greer 25 1 1 1 Filip Wahlberg 26 1 1 1 Nerd1729 27 1 1 1 Mtcv 28 1 1 1 Luciferoussky72 29 1 1 1 AgentMuffin 30 1 1 1 Geminga 31 1 1 1 Jordan Olling 32 1 1 1 Xkdvd 33 1 1 1 1234231587678 34 1 1 1 Mushrooms 35 1 1 1 Lordpishky 36 1 1 1 King Pando 37 1 1 1 Martin 38 1 1 1 Malgond 39 1 1 1 Qwertyuiopfromdefly 40 1 1 1 Pie Guy 41 1 1 1 John Early 42 1 1 1 Jack