Jay is only ninja to appear every episode due to the events of Season 6. Before that, Nya was the only one not to appear in every episode due to the events of the pilot.
In episode 2 In the US/Canadian version, Zane left a message in the fridge. However, in the variable language variation, he is actually sitting inside of the fridge when responding to Kai's reaction
This series timeline is seperate from the film universe.
In the rebooted series, the Nindroid's mask left eye has 3 laser pointed dots which is similar to the original 1987 predator's laser cannon having 3 laser pointed dots.
The name Kai means "strong," "victorious," and "recovery," in three Asian cultures, all of which fit his hotshot attitude in the Ninjas' battles."Kai" may also be derived from the Japanese word Akai, meaning "red."