And here's another- Nivawk.
All Nivawk EVER did in the ENTIRE story was tell Teridax about the Toa Metru's transformation (which he already KNEW was going to happen when he planted their names into Lhikan's head), report on Nidhiki and Krekka's battle with Vakama, Nokama, and Matau on the airship, and later their break-in into Lhikan's prison; Both of which are easily done with generic Vahki, or some other plot device.
Point in case- Nivawk was a plot device, but even WORSE than the regular one, because his function in the story was so pointless (due to how few things he did, and how little importance these acts had) that his ONLY actions and prevalence in the story is to just BE there when something happens.
All Nivawk really did was just fill in a space for the Titan sets of 2004 and add wings to Teridax in the movie that just made people confused (unless they read Time Trap).
Also, I just realized that this WHOLE topic is basically dissing several characters' meaning and existence.
Edited for double-post. If you're confused about what that means, please take a look in here. --John Smith