Additional Behind-the-Scenes Footage
On the second page of [Special Features] you can highlight the Pyramid. This will allow you to watch more additional behind-the-scenes footage.

If you highlight the hidden elements in the [Cast & Crew] section you will get to see a stunt test clip, and in the [Languages] menu you can access yet another stunt test clip.

If you watch the film with the audio commentary on, occasionally a Psychlo letter will appear on the screen. Selecting it will then take you to some behind-the-scenes footage of that particular scene.