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 5,737 5,718 5,807 DollarStoreBa'al 2 1,922 1,903 1,993 Victoria 3 17 14 17 TheusafBOT 4 11 5 14 Trimutius 5 10 7 10 FaviFake 6 9 6 8 Utdtutyabthsc 7 7 4 7 Lp0 on fire 8 7 5 6 R128 9 7 2 8 boB 10 6 3 6 BunsenH 11 5 3 4 Headphones the stickman 12 4 1 4 NotBob 13 4 2 3 Fephisto 14 4 2 3 Barry Margolin 15 3 1 2 Kynde 16 3 1 2 Kirinhatchi 17 3 3 3 Batbrain55 18 3 1 2 Stephan Leeds 19 3 3 3 Starnote 20 3 1 2 Beechmere 21 3 1 2 TheSeventhElectron 22 3 1 2 Questioner 23 3 3 3 KelOfTheStars! 24 3 1 2 Paul 25 2 2 2 RadiantRainwing 26 2 2 2 August Fuller 27 2 2 2 CalibansCreations 28 2 2 2 AgentMuffin 29 2 2 2 Theusaf 30 1 1 1 DKMell 31 1 1 1 GreatWyrmGold 32 1 1 1 1234231587678 33 1 1 1 Coconut Galaxy 34 1 1 1 Dbwiddis 35 1 1 1 Cobl703 36 1 1 1 Planer28 37 1 1 1 Not without text 38 1 1 1 David Garfield 39 1 1 1 Daniel Griscom 40 1 1 1 Bdentremont 41 1 1 1 Geometrist 42 1 1 1 StepSquadStepped 43 1 1 1 I’m gonna fix this 44 1 1 1 Nvidietha 45 1 1 1 183231bcb 46 1 1 1 Magtei 47 1 1 1 Michael Valler 48 1 1 1 Mathmaster 49 1 1 1 Ardub