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 7 1 11 GSLikesCats307 2 4 2 3 YZ100 3 3 1 2 Paul 4 2 2 2 FaviFake 5 2 2 2 Barry Margolin 6 1 1 1 Michael Thomas Greer 7 1 1 1 Cy1110 8 1 1 1 Chronotix 9 1 1 1 Scs 10 1 1 1 Kirinhatchi 11 1 1 1 DKMell 12 1 1 1 Quincy 13 1 1 1 Alexei Kopylov 14 1 1 1 BunsenH 15 1 1 1 Paul Nickerson