What to put on the back of a t shirt?

it's for this charity event for teenage cancer and everyones got t shirts at school and they're like cutting the sleeves off and writing on the back like '<---- I'm with stupid' and stuff, me and my friend might be writing 'twiddledee' on one and 'twiddledum' on the other but not sure so does anyone have any ideas for the back of my t shirt?! thankyou! it's for charity!x