Many years ago when on B707's with Kuwait Airways we for the first few years always did our base checks on the aircraft. We got airborne with full fuel and about three of us for checks doing circuits and go arounds when we heard a banging noise. The F/E went down to the Lower 41 and peered through into the cargo hold and saw a pair of eyes staring at him. We landed and let out a Baluchi baggage loader who had gone in to get out of the sun. We couldn't stop laughing for the rest of the exercise