For crazy hair day we colored his hair with blue chalk. We wet it first a bit where we wanted the chalk to go and then just rubbed it on. It worked really well and by the end of the day it was mostly faded out.
For sports day was there ever any question as to what he'd wear? Jersey, hat, t-shirt and pants. I had a hard time convincing him that he couldn't wear his football helmet to school. Funny kid!