Pirate and Mermaid Invitation Pirate and Mermaid Double Birthday: Ahoy there! This absolutely awesome invitation features a pirate on an island with his treasure. Also a mythical mermaid playing her harp on a wave. A wonderful invitation for a siblings joint party. Suitable for girls or boys. It invites their friends to choose to dress as whoever they like, a pirate or a mermaid. Don't be a fish out of water this pirate mermaid invitation is just the right invitation for a birthday extravaganza!