invitation idea's, please help!?!

My eighteenth is coming up and I've decided to have a masquerade theme, were everyone turns up wearing a mask! I'm doing up my own invitations but I'm kinda stuck.. I wanted a little poem or something that's telling everyone to wear a mask and to dress up a little.. I've got all the other details written out, just need a little help with telling everyone bout the theme.
can anyone help me?
please and thank you!