...What?
You have a copyright lawsuit in the works? You do realize the title is quite generic, yes? Adding "zombie" to "spongebob" has been done before this or HDD's work, so it's bound to be that somewhere, someone will have the exact same name and the exact same idea, but both your pictures are quite different.
See, you've got a bit of a story going on, while HDH's just has Spongebob bein' Zombob (Heh, see what I did there? Yeah. I gotta write that down!).
I'm not trying to make you mad, you have a very good drawing, but you kinda jumped the gun a little with the anger thing...
...
I haven't been able to watch Spongebob in six years. It still gives me nightmares...