I'm Not Sure What to Wear For Pajama Day?

Okay, so Monday is Pajama Day (its Red Ribbon Week in my middle school, so Monday is Pj day) and I'm extremely confused on what I should wear! I have a pair of grey yoga pants from Pink, and then I also have a pair of pink and orange plaid pants from Victoria's Secret. Im not sure what shirt I should wear..i have a big black tee shirt that i cut and tied, or should I wear a tank top? Also...slippers??