halloween costuming-need advice!!

OK, gonna do the Halloween thing next Wednesday...and trying to think of a costume-definitely NOT repeating my costume from 2 years ago...

Anyways, talking to my colleague, and was thinking of wearing one of my running skirts and she was like-"just pin on a number and you can be a runner-easy and cheap idea for a costume."

And you know what? She's right.

So...I am coming to you, my readers, to help me complete my outfit. I was thinking running skirt (most likely one of the ones from runningskirts.com)...maybe with thigh-high socks? What kind of top? Anything else that comes to mind? (And before any of you men say it-no jogbra.*)

*EDIT-what I meant there was don't tell me to wear just a jogbra. And inspired by the smartass comments I have received so far...don't tell me to go topless either :-p