"Simon the Crab" joke

Simon the humble Crab and Kate the Lobster Princess were madly, deeply and passionately in love. For months they enjoyed an idyllic relationship until one day Kate scuttled over to Simon in tears.
"We can't see each other any more..." she sobbed.
"Why?" gasped Simon.
"Daddy says that crabs are too common," she wailed. "He claims you are a mere crab, and a poor one at that, and crabs are the lowest class of crustacean and that no daughter of his will marry someone who can only walk sideways."
Simon was shattered, and scuttled sidewards away into the darkness to drink himself into a filthy state of aquatic oblivion.
That night, the great Lobster ball was taking place. Lobsters came from far and wide, dancing and merry making, but the lobster Princess refused to join in, choosing instead to sit by her father's side, inconsolable.
Suddenly the doors burst open, and Simon the crab strode in.
The lobsters all stopped their dancing, the Princess gasped and the King Lobster rose from his throne.
Slowly, Simon the crab made his way across the floor, and all could see that he was walking, not sideways, but FORWARDS; yes FORWARDS, one claw after another!
Step by step he made his approach towards the throne, until he looked the King Lobster in the eye.
There was a deadly hush for quite a while.
Finally, the crab spoke - "Bugger, I'm pissed."