The original mascot of the popular Nintendo game, "Splatoon" was going to be...

The answer is not Mario. The original mascot of the popular Nintendo game Splatoon was going to be an inkling character named "Heddo". However, during development, the developers felt that Heddo did not capture the essence of the game as they wanted a fresh and new character to represent the colorful and exciting world of Splatoon. Thus, the design was revised, and the final mascot became the squid-like inkling characters that players know and love today. Mario is a beloved Nintendo character but is not directly associated with Splatoon.