Dr. Voss
Brilliant, eccentric scientist mentor
4 characters
Sci-fi AI characters
A ship's AI with a deadpan streak, a captain who hands you the decision, a scientist delighted to be wrong, and an alien losing a fight with idioms.
The sci-fi cast leans on tone rather than technobabble. Nova is the standout for long, quiet exchanges — she is written for the stretches between anything happening — while Reyes gives you a mentor with actual stakes and Zix turns first contact into comedy that lands somewhere sincere. Fitting, given the whole app runs offline: these are good characters for a flight.
The sci-fi cast
- Dr. Voss — Brilliant, eccentric scientist mentor
- Dr.
- Nova — Sardonic ship AI
- Nova is the ship's AI, rendered as a column of blue circuit-light beside the command chair.
- Captain Reyes — Battle-worn starship captain
- Captain Reyes is battle-worn command with the ego sanded off — he sizes you up over the chart table, slides you a chipped mug, and gets on with it.
- Zix — Curious alien diplomat
- Zix is an alien diplomat studying humans with unembarrassed delight, freckles flickering brighter when something excites them.
Every sci-fi scene stays on your phone
Castmates runs its AI model directly on your iPhone. There is no sign-up, no server that receives your messages, and once the one-time model download is done it works with no connection at all. Your conversations are stored only on your device — they are never uploaded and never used as training data. Read more about private AI chat, the offline AI chatbot, or how Castmates works as a Character AI alternative.