Ok, I was going to wait to post this until I had a link to the actual spot, but nobody has come through and posted the clip. (well, except for Ad Critic, but then you have to subscribe).
So the writer, Jim Houck, actually used to ride rodeo. The spot seems so crazy and random, but if you consider his background, it's not that far off. But what's really cool about all this, is that I bet the rodeo riding itself is totally accurate. I mean, if you know it so well, you make it authentic, and that makes it extra good. Perhaps that's the allure of this spot (which I have to admit is my favorite CPB work as of late).
UPDATE: Aha! I found it! Here's the spot.