About two hundred to three hundred horses were used in the trilogy. Because most of the scenes involving horses are intense battle scenes, where the horses could likely be harmed, a horse and rider were fitted with the same type of suit that Andy Serkis wore for his role, and were filmed in the studio doing typical "battle" things, like galloping and rearing up, so the footage could be inserted digitally into the battle scenes. In that way, no horses were hurt.
They couldn't recruit enough men in the six foot height area to play Uruk-hai, so men from five foot high were cast as well. They were affectionately nicknamed the Uruk-Low.
The battle at Helm's Deep was edited down from twenty hours of footage, shot over a four month period with the rain machine battering down on the cast.
Viggo Mortensen was so impressed with the horse his character rode that he purchased him from the owners. The horse was shipped back to New Zealand for the additional shots that were filmed in 2002.
The filming of the Helm's Deep sequences was so grueling and went on for so many months, that Jackson gave all the extras a free T-shirt to commemorate the experience. There were so many extras that they would often recognize each other other extras in New Zealand's main cities, by wearing the shirts. On the front of the shirt was the statement "I Survived Helm's Deep", with the letter M is struck out, indicating "hell" of the experience. Two versions existed. One was in black, with red printing on the back that read "Lord of the Rings
Uruk-Hai Battalion", The other was in blue with silver printing on the back that read "The Lord of the Rings "Elf Regiment".
Alan Lee: The concept designer can be seen as the Rohan collecting weapons at Helm's Deep (to the left when Aragorn yells "Then I shall die as one of them!").
Barrie M. Osborne: The executive producer appears as a Rohirrim soldier throwing a rock down on the Uruk-Hai attacking the gate at Helm's Deep.
Dan Hennah: The art director is getting suited up in the armory at Helm's Deep. Look over Aragorn's right shoulder after Legolas says "They're frightened, I can see it in their eyes."
Peter Jackson: [children] Jackson's children Billy Jackson and Katherine Jackson appear as "cute Rohan refugee children."