OH MY GOD. The game SHOULD have been about killing them!
That actually solves most of the design issues.
What can you expect from something with such a stupid title? Well, let me tell you.
Bouncing Bass Brawl Bonanza is a couch multiplayer game about buff fish that forget who their teammates are. What a mouthful. It's not an easy game to pitch, if I'm honest. The trailer explans the concept much more clearly.
It's free and you can play it on your browser. Play it with your friends! Play it with your mum! (let her win)