Ran into a fleet skin that's not in the shop?

[Gecko]

It was like purple with a bird face on it, and the bow had a big pawpad mark in the middle. II didn't see it in the shop, what's up with it? Is it mods, or just secret? had star particle effects too

[Songbird]

A modded skin would be client-side only and not show up for you online.

That skin is Pajama Fleet, and along with Princess Fleet and and Fan Fleet, it exists in the game files but can't be obtained normally. Might have been someone on a dev build or something?

https://rivalsframedata.com/skins/Fleet