Admitted I agree, the shark lawyers will eat him alive. But he does have a point that it was a people that made that left shark famous. Had it not been for his comical and lethargic performance no one would have paid any attention to that shark and it would be a quickly forgotten memory. This is pretty much left shark's 15 minutes of fame.
But I'm willing to bet this is just some lawyers seeing cash in their eyes being the greedy SOBs they are, I'd like to think Katty Perry could careless about some silly shark. But if I may be so bold to say it, the shark costumes were not very original anyways. They remind me of Khurasan Miniatures Karkmarine miniatures.
I'd like to see a counter sue, but Khurasan wouldn't have the money to do this. So it comes to a question of how many different ways can you make a shark costume?