"Fuck the world" is a running gag of the Creatures. It was created (and mostly used) by Nova. The character (it can be any) picks up their own leg and throws it in the air while shouting "fuck the world".
On November 27, 2011, Nova posted a Happy Wheels video; around the 4:16 mark of the video, Nova chucked his leg and said "Fuck the World". Since then, most of Nova's Happy Wheels videos have had that saying in it, and it even has its own t-shirt.