Hello there! Which scene or animation you unlock upon game over is purely random. You can try unlocking others by intentionally dying (in game).
Hello there,
I've investigated the issue, and indeed, there was a minor bug affecting the chance of unlocking new animations, particularly if you were killed by a muscly. However, it's still possible to unlock others, albeit with some difficulty. In your case, it might be a combination of bad rng + this bug. Fortunately, it's already been addressed in the upcoming public version. While I could roll out a fix, but it will take too much time for a small bug (compiling took hours).
Thank you for your patience.