There were two prawns, James and Christian, swimming along the bottom of the ocean. James accidentally rubs up against an old lantern and whoosh, a magic Cod fish appears and grants him two wishes.

After a moment's thought James decides that he wants to becomes a shark so as to gain the respect of all the creatures of the sea.
Whoosh, James becomes a shark and swims off.

Two weeks later James is upset. All of his old friends are now afraid of him and his life is miserable.
He decides to use his second wish, and he wishes to be a prawn once again. He spends the next two weeks trying to find the magic Cod and when he does....... Whoosh.... now a prawn once more, James swims away to look for his mate Christian.

When he arrives at Christian's house he knocks on the door and shouts out for Christian.
"Go away", says Christian, "You're a shark and you'll just eat me".
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"No I won't", shouts James, "I've found Cod. I'm a prawn again Christian".