Yip yip!
Appa is a Flying Bison from the Nickelodeon televison series Avatar: The Last Airbender. During the events of this RP, Luna apparently stole Appa from Aang and made him into her own personal means of transportation. Despite this, Appa is loyal to Luna and the princess treats him well.
During Chapter II, Luna used a polymerization card from Yu-Gi-Oh to fuse Appa with Lupez's pirate ship, the Kreamkken, forming a new ship known as the S.S. Appa. Despite being fused with a flying pirate ship, Appa's soul remains alive within the vessel and is essentially still a living being, making the S.S. Appa difficult to control at times. Appa now serves as Smoosh's main method of transportation as well as their home.