Harold is new to the school. He has no friends and none of the other white sharks want to play with him because he is very small and different from everyone else. He sees a group of crabs, and them too start bullying Harold.
Harold it's you?!
When Harold gets home he comes up with a great idea and decides to dress up. Harold wanted to show that everyone was the same and equal.
The next day at school he came to school dressed up in a costume, he was the "biggest" shark of them all. Everyone in school admired him and how big he was, he was also funny with a great sense of humor so everyone fell in love with him immediately.
At the end of the day when Harold took off his costume everyone realized it was him, the same old Harold. But what they also realized was what a great person he was even if he was small, that didn't matter anymore because he was a great person.