Reality Subtext: Happens a number of times, most memorably and effectively when in book two Omri tries to bring Tommy back to heal Little Bear, only to find he'd been killed in World War I, and again in book four when awakening the figures belonging to Jessica Charlotte reveals Sergeant Ellis died at Trafalgar. The last book, dealing with the Real Life fate of the Iroquois versus the American colonists, is even more about this.
No Export for You: The 20th Anniversary Edition was only released in the US as a region-locked Blu-ray.
Shown Their Work: Omri starts out with a child's typical amount of knowledge of Native Americans. When he offers Little Bear a tee pee to sleep in, Little Bear is understandably confused, as Iroquois lived in long houses.