Haha! I didn't think you could mix it either, but then I heard that they do it in britain and decided to try it. Have you ever tried it? It really, truly just tastes like coke. And, like I mentioned before, very few calories.
How is it any different from a rum and coke or a jack and coke? I drink those too. I just happen to have vodka and diet coke at my house tonight. I also have tequila, if you can think of anything good for that.