Then the best you can do is 1) emphasize why you didn't do so great in your classes, and 2) convince them that this won't be the case in b-school. I tend to agree with your philosophy about some of those extracurricular activities being more valuable to you. I think you can argue that this was the tradeoff you made. To point #2, I think those clases that you've taken recently will help a lot.
In terms of how long ago it was, that's sort of true. Really, the less work experience you have, the more they need to rely on your schoolwork to gauge your potential. The more work experience you have, the more they'll rely on that. So, it's less about how long ago that was, and more about whether or not they have better info to go on.
Re: comedy, you can DEFINITELY use this to your advantage in your app. How many b-school applicants are accomplished improv performers?? This kind of uniqueness will be really interesting to a weary adcomm who's just read 20 apps in a row. Don't be afraid that it sounds too un-MBA-like or not serious enough... Nonsense! Show that you're comfortable in your own skin, with laughing at yourself, etc. Explain WHY you like it, and show your passion for it!
Scott
_________________
Co-Author, Your MBA Game Plan