How can you be a mermaid and fairy in the sims 2?

You can't really be a mermaid or fairy on Sims 2. But go on modthesims2.com or go to a downloading place for sims 2 and there should be a mermaid or fairy COSTUME. Download that and go to one of the stores in the town. The costume should be there and so buy it. Then go to your dresser at home and put it on.