From the disc's main menu go to the 'Extra Features' menu. Highlight the entry 'Movie Stills' and then press the arrow up key on your remote control. This will bring up a fork and a knife. Now, press 'Enter' and you will be taken to a map entitled 'Trail of the Donner Party 1846.' On that map, repeatedly press the left arrow key and you will highlight a trail with dates. At 'Fort Bridger July 30', press the arrow up, and another knife and fork will appear. Press 'Enter' and you will see the credits for the disc's developers.
If you go all the way past Fort Bridger until you reach 'Truckee Lake October 30: Donner Camp,' press the arrow up key there and yet another knife and fork is highlighted. Press 'Enter' now and it will show you an advertisement for 'Ravenous Beef Jerky', an actual promotional item.