Many orbits around the sun have passed, but I am pretty certain this Tweek from around 2016 is by Mad Tuna who did post some South Park fan art in the long long ago. (I think the Twitter account I found is the same person!)
I’ve always loved her interpretation of Tweek, especially the almost chalk-line like style for the line art in this illustration.
Artist: Mad Tuna @Atun_de_Marzo | https://x.com/Atun_de_Marzo