What's up dude??

During snack time in the preschool classroom, one of my speech students finished his snack and figured it was time to go play.  The paraprofessional encouraged him to stay a the table and talk with his friends.  To which he proceeded to place both hands on the table lean forward, and ask the child sitting across from him, "What's up dude?"  The other student looked at me confused and asked, "What'd he say?"