Aggy Boo is a term said in the town Middlesbrough. It is used when someone has had something unfortunate said or done etc to them.
It is used as a "the jokes on you" kind of way...Devastated if you will.
Bill-o - " Shit, i left ma phone in ma trousers. Its in the fuckin washer now."
Benzy - " Ahahaha! Aggy Boo mate!"