The Rainbow Fish
If you read The Rainbow Fish growing up, it shouldn’t be difficult to figure out this costume. Evidently, this girl decided to dress up as the unique fish from The Rainbow Fish, a German children’s book and a children’s TV series of the same name. If you aren’t familiar with the book, it tells the story of a fish that had unique, shiny scales, quite similar to this girl’s costume.
He was reluctant to share his shiny scales with his friends, since he feels as if they make him unique, until he finally realized his friends are worth a lot more than shiny scales. Ultimately, the moral of the story is teaching children about the importance of sharing. This girl must’ve been a fan of the book growing up, as she looks just like the shiny fish from the illustration cover.