I have a friend who was told in 3 ultrasounds thru her pgcy that she was expecting a girl. Labour came and out popped a boy! Boy was her family shocked and they all had to run out and buy boys clothes Hehehe!
Yes, being told a boy generally means they can see the unmistakable willy and boy bits, being told it's a girl, generally means they "can't see" any obvious boy bits so they assume it's a girl. Mind you, they were right with both of mine!