Hello Chaoticlock,
This is a source of confusion for me as well. After reading your post I dropped a Changing Booth device into my TMNT level, but I’m not seeing any turtle skins to select. I don’t think that a ‘temporary skin’ system even exists in Fortnite, so playing as a turtle without owning the skin probably is not possible.
For animatics - in the TMNT Content folder there is a ‘TMNT Character Spawner’ Device where you can spawn the turtles as hireable guards, but I’m unaware of a way to play your own animations on them. (Also noticing that the turtle IP is absent from the NPC Spawner devices ‘NPCCharacterDefinition’ cosmetic selection.)