Nova M Bajamonti / HELLO!: Who is Kat Stickler, John Mayer's supposed new romance? - The "Waiting on the World to Change" singer was spotted hanging out with Kat two nights in a row in New York City. Find out all about his mystery girl. - (C) Getty Images - John Mayer has been getting close with his suppossed new romance Kat Stickler.