According to Zane's voice actor Brent Miller, he wasn't originally supposed to be a robot. However, at some point (presumably during the development of Season 1) the writers thought that Zane's stiff design coupled with Miller's detached tone made the character seem robotic, and decided to incorporate it into the show.
Zane's Father, voiced by Mark Oliver, is listed as such in the credits for season one, but as "The Tinkerer" in season 2, and finally "Dr. Julien" from season 8 onward.
The woman Wu buys Traveler's Tea from, listed as "Old Woman" in the credits, is later named as Mystake.