I see lots of people dressing up for races. I shy away from using the word ‘costume’ unless they look like superheroes, pieces of fruit or a shower–and yes, I once actually saw a man dressed up as a shower, curtain and all, during a race. Anyway, unless I see someone costumed like that, I just think of them as dressed up.
When I notice dressed-up people, I will wonder if she can run comfortably in those stockings. I think about the center of gravity when a man with a ten-foot tall hat runs by me. Or I may wonder about whether the man in the banana suit standing in the port-a-potty line will have enough room to handle his business. Those are the things I wonder about.