Upon first reading about this, I admit I thought it was absurd, as did many other animators and cartoon aficionados. But upon second thought, this idea of "arenas" is an excellent starting point for story ideas. And getting started with generating ideas is half of the challenge.
Method 1 for generating story ideas: make a list of all of the places where a story can occur. He's a partial list I made two years ago:
This list ended up being about 3 pages. I actually got the idea for my current project from this list! So although this method may seem silly, its success is measured by how effective it is in getting you closer to your goal.
Method 2 for generating story ideas is described here—in comic book-like fashion—by Frank Chimero, graphic designer and illustrator. Here's a sample:
Basically, he encourages alogical yet meaningful connections. Ya gotta read it to get it and once you get it, you'll never find yourself wanting for an idea again!