Oh, boy.
1. Inf. Wow! (Usually Oh, boy! An exclamation. It has nothing to do with boys.) Bill: Oh, boy! An old-fashioned circus! "Oh, boy!" shouted John. "Dinner smells great! When do we eat?"
2. Inf. I dread this!; This is going to be awful! "Oh, boy!" moaned Fred, as his old car stalled out, "Here we go again." Doctor: It looks like something fairly serious. Jane: Oh, boy. Doctor: But nothing modern medicine can't handle.