How legally distinct would a Homestuck ripoff need to be to pass? (Theoretical question)

I'm not actually going to do this, I'm just dying for an answer. And maybe someone else will take the bullet and make it free for the people.

I understand that there's not a lot to exploit here and that it'd be pretty easy to sue off the face of the earth in a lot of cases. But like, there has to be some way, right? It's not like the idea of a Homestuck story is copyrighted.