I tried to find something about it online, Big Buck Bunny is a movie that came out like 16 years ago I think and is popular because it serves as a universal, open-source benchmark for 3D animation and video testing, and the video you saw in that folder was a sample, my best guess is that it came with Unity (Game engine used to make Starmaker Story) by default, Unless I am wrong about that and the devs used it somehow .