Before the singular story concept of Sonic fighting against Dr. Robotnik, Sonic's character development was very different. During the 2018 Game Developers Conference, game designer Hirokazu Yasuhara and character designer Naoto Ohshima revealed that the series almost had connections to World War II.

"Sonic" was originally going to be a fighter pilot who earned the nickname "hedgehog" because of how his hair stood up while flying his plane at high speeds, while the Sonic the Hedgehog design known today was merely a nose decal on the front of his plane. The details of his time in the war were then re-imagined as a children's picture book by the pilot's wife. She took the Sonic the Hedgehog design and based it on her war veteran husband, making the game a story within a story. American pilot Chuck Yeager, the first pilot to break the speed of sound, was also mentioned in Yasuhara and Ohshima's pitch summary.

Additionally, they showed off line art for a proposed dance sequence during the game, originally intending for Sonic to be a trendy dancer, but this along with the meta-story elements were scrapped during development.

In the third installment of the Untold History of Japanese Game Developers book series released in 2018, Ohshima reiterated that Sonic was going to be a human boy, but SEGA rejected the design, not wanting their mascot to be a human, and Ohshima admitted that he does not have any concept art of Sonic as a human due to his proposal just being a basic outline. Despite this rejection, the core layout of Sonic the Hedgehog's speed-based gameplay and map design was set in stone by this time.