After defeating a boss in a hub world, a cinematic will play where Ninja collects a Rage Stone from their guardian. There are early takes of the voice lines for these cinematics left over in the game's files.

At one point, a sequel to I-Ninja was in development, but was ultimately cancelled (likely due to the liquidation of Argonaut Games). Concept art for the game was released, notably featuring a military theme compared to the original, with both the Ranx and the Kappa Captain getting redesigns, a new enemy called the "Top Droid", and various props and weapons. Additionally, it seems that the sequel would have featured Halo, a character that was supposed to appear in the original game as the Ninja's girlfriend but was ultimately scrapped.