They mixed together alright. They looked ok when I spread them in the pan. It even smelled right baking. However when I went to get them out of the oven, the top was dull not glossy, they had barely risen at all, and you know how they pull away from the sides of the pan when they're done? These looked like they were horribly afraid of the sides and had run as far as they could from them. There was a half inch gap all the way around. I cooked them 10 minutes less than the brownie mix said so they weren't over done. They weren't burnt. So I let them cook and lulled myself into the belief that looks can be deceiving and decided to I'd try them later.
Oh. My. God. They didn't taste like pumpkin (which they weren't supposed to so that was good) but they certainly didn't even taste like chocolate either. By far the worst part was that they had the consistancy of a Good Year retread! You've never seen such a wicked mess of crap in your life. Ben wasn't even interested, and he's been known to eat poo on occassion. I dumped the whole mess in the trash and thanked my lucky starts that I hadn't lost the pan along with the experiment.
So here's the lesson. You can mix pumpkin with a cake mix with great results. You can mix diet pop with a cake mix with great results. And although you CAN mix pumpkin with a brownie mix, for the love of G-d people, it is not in anyone's best interest to do so. Once again, I perform these experiments so you don't have to!