Split P Costume
Cut out a large p from a piece of colored construction paper (green is the obvious first choice, but any color of paper will work in a pinch), and then cut it in half. Tape each half to either side of a zippered hoodie, so that the zipper appears to slice through the letter. You could use a hot glue gun instead, but that’s, unfortunately, a bit more permanent. And just so you don’t have to field questions all night long, ensure everyone gets the joke by carrying a can of split pea soup along with you for the evening.