Here's another prawn story, as told by David Niven to Dame Edna Everage on her TV show (as best I can remember it):

Once upon a time at the bottom of the ocean, there were a young female prawn and a young male crab. Now, prawns and crabs usually don't have much to do with each other, as prawns particularly dislike the way crabs walk sideways. However, the young lady prawn was not prejudiced, and she and the young gentleman crab struck up a relationship.

Eventually, she plucked up the courage to tell her parents that she was dating a crab. Of course, they were horrified and said, "Why on earth do you want to go out with one of those awful crabs? They can only walk sideways, for goodness sake."

But the relationship grew stronger, and after a time the prawn's parents reluctantly agreed to invite the crab over for dinner. The crab was very nervous when he heard this, as he knew how much prawns disliked the way crabs walk sideways and wondered what he could do to make them like him.

Anyway, on the big night, the crab showed up at the prawns' front door, and stunned everybody by walking straight forwards into the room! After a while, the young lady prawn managed to get the crab into a quiet corner and whispered to him, "How the heck did you do that? You walked straight in the door and didn't go sideways."

The crab whispered back, "Shhhh! I'm drunk!"