I don't usually do this but...

 swimming  around in the sea, one called Justin and the other called

 Christian.    The   prawns   were  constantly  being  harassed  and

 threatened by sharks that inhabited the area.

 Finally  one day Justin said to Christian, "I'm fed up with being a

 prawn;  I  wish I was a shark, and then I wouldn't have any worries

 about being eaten."

 A large mysterious cod appeared and said, "Your wish is granted."

 Low and behold, Justin turned into a shark.

 Horrified,  Christian  immediately swam away, afraid of being eaten

 by  his  old  mate.  Time passed (as it invariably does) and Justin

 found  life as a shark boring and lonely.  All his old mates simply

 swam  away  whenever  he came close to them.  Justin didn't realize

 that his new menacing appearance was the cause of his sad plight.

 While swimming alone one day he saw the mysterious cod again and he

 thought  perhaps  the  mysterious fish could change him back into a

 prawn.   He  approached the cod and begged to be changed back, and,

 low and behold, he found himself turned back into a prawn.

 With  tears  of joy in his tiny little eyes Justin swam back to his

 friends  and  bought  them  all a cocktail (the punch line does not

 involve  a  prawn  cocktail - it's much worse).  Looking around the

 gathering at the reef he realized he couldn't see his old pal.

 "Where's Christian?" he asked.

 "He's  at home, still distraught that his best friend changed sides

 to the enemy & became a shark," came the reply.

 Eager  to  put  things  right  again  and  end  the mutual pain and

 torture,  He  set off to Christian's abode.  As he opened the coral

 gate,  memories  came  flooding  back.   He  banged on the door and

 shouted:  "It's  me,  Justin,  your old friend, come out and see me

 again."

 Christian replied, "No way man, you'll eat me.  You're now a shark,

 the enemy, and I'll not be tricked into being your dinner."

 Justin  cried  back  "No,  I'm  not.   That  was  the old me.  I've

 changed........."