The character Kiina was originally to have a heavy Russian accent, but it was given to Strakk instead.
Even though one might think that, due to his voice and the way he speaks, Gresh is the youngest Glatorian of the movie, it is in fact noble and deep-voiced Mata Nui, being "only" a hundred thousand years old. Gresh was already around by the time Mata Nui came into being.
During the fight with the Skopio beast, you can clearly hear it making Godzilla's distinctive roar.
The animators went to great lengths to make the movie characters look as close to their toy counterparts as they can. In the first three Miramax-produced Bionicle animated movies, muscle and flesh were added to the otherwise mechanical looking characters, and some of their other features have been tweaked as well to make them look more like living beings, rather then robots (they were given fingers and mouths, for example). That is not the case in this movie - the characters even have the pins and axles showing that keep their bodies together, and they also wear a life-counter gear, something that was originally meant to be a toy-only feature. But to be able to emote better, their helmets can retract the parts that cover their mouths, and eyebrows were also added to them.
The reason as to why the characters use Thornax launchers so sparsely in the movie is because the design of the launchers had not been finalized yet when the production has already began. The ammunition is also depicted as explosive, glowing orbs crackling with energy, rather than the simple round, spiky and rarely explosive fruits that we see in the comics and books.