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 1,414 1,405 1,424 DollarStoreBa'al 2 65 63 64 Victoria 3 3 1 2 Questioner 4 3 1 2 Stephan Leeds 5 3 1 2 Trimutius 6 3 3 3 R128 7 2 2 2 Lp0 on fire 8 2 2 2 boB 9 1 1 1 Cobl703 10 1 1 1 Michael Valler 11 1 1 1 KelOfTheStars! 12 1 1 1 August Fuller 13 1 1 1 Starnote