"are you crazy?"
if it's a stranger or another adult you hardly know - Sind Sie verrückt?
if it's a friend, someone you know - Bist du verrückt? / Spinnst du? / Hast du sie noch alle? (a bit more informal)


About "Shee Oouf." - Sorry, but I have absolutely no idea. Not even a hunch. Could you say sth about the context when you heard it?