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 5 8 YZ100 2 3 1 2 Paul 3 1 1 1 Alexei Kopylov 4 1 1 1 Michael Thomas Greer 5 1 1 1 Chronotix 6 1 1 1 Velocifyer 7 1 1 1 Quincy 8 1 1 1 Scs