You shouldn't change the first character in a fake collab because it completely breaks the continuity and the element of surprise that makes these dynamics so much fun. In Castle, the heart of a fake collab is seeing how each creator reacts, adapts, and adds their own unique touch to the scene left by the previous participant. If you restart the chain or change the main character from the beginning, you're ignoring the work and narrative thread that everyone else painstakingly developed. You lose that organic flow of animation. Instead of changing it, the ideal approach is to work with what already exists and use your creativity to interact with that first character, whether by launching a counterattack, a visual remix, or a fun twist in the script. Keeping the original foundation respects the community collaboration and challenges your skills as an animator much more. Give the core idea a chance, and you'll see that the final result is much better for everyone!