Character Creation in the Celestia campaign has two parts: your physical self and your game persona. In fact you can have more than one game persona, though one should be primary.
Since most of the action takes place in the game world, your physical self is most needed for social skills. However it needs to be built as normal for a Fate character, because some of the action does not take place within the game world and having a wider selection of skills is very important. Crossover characters take on the physical skills of their Celestia persona on top of the base skills.
Game Personas are made in the image of the Celestia game itself. The game doesn’t have social skills and is focused on combat with very fixed move lists.