Cowboy BeBop at His Computer: In a very odd attempt to tie-in the game to the DiCSonic the Hedgehog cartoon, Amy Rose is inexplicably referred to as Princess Sally in the North American Sega CD manual, even though Sally has never appeared in the games,note Sans a blink and you'll miss it Early-Bird Cameo in the Sonic Spinball bonus stages. and Amy looks and acts absolutely nothing like her. The PC manual corrects this mistake.
Or rather, cut segments of a song, as early prototypes had what appeared to be unused in-game music loop pieces that would apparently inconspicuously play while the CD track ends and re-loads from the beginning. May have been removed due to time or inability to perfect this feature, but it was restored in the 2011 remake.
In the pre-release, the title screen and Speed Up tracks were totally different, and the Special Stage song had an extended cut.
A rather odd example occurs with the American version. Within the CD audio tracks, there's a duplicate of the title theme.
Development Gag: During the Special Stages from unfinished pre-releases, a Engrishy message appears on the screen, telling the programmers to wake up and finish their jobs:
"Toot Toot Sonic Warrior" for the Japanese/PAL opening theme.
The secret Special Stage is sometimes referred to as "Eggman's Bathtub".
Some fans have changed what "CD" stands for in the 2011 remake, such as "Completely Digital" or "Console Download".
Keep Circulating the Tapes: The original Sega CD version suffered from this.note Not the PC version. It was going to be included with Sonic Mega Collection, but it was cut because Sega didn't have documentation on the Sega CD. It was eventually included in Sonic Gems Collection, ported from the PC version. Eventually, Sega hired Christian "The Taxman" Whitehead to recode the game from scratch for the 2011 remake.
Killer App: If it wasn't one for the Sega CD, it was one of the closest things it had to one.
No Export for You: The Japanese version's soundtrack wasn't officially released worldwide until the 2011 remake, which has both that soundtrack and the US version's, by members of the Sega Technical Institute. It was long rumored that licensing issues were holding back such a release, but Word of Godhas it that the remake almost didn't have the US soundtrack because of licensing issues.
Polished Port: The 2011 remake, which not only updated the game for HD but also includes both the American and Japanese soundtracks, has the Sonic 2 Spin Dash as an option, and has Tails as a playable character.
Promoted Fanboy: Whitehead, who did the downloadable remake. He was responsible for creating the Retro Sonic engine, a number of fangames, and is also a member of the Sonic Retro community.
Whitehead: Yeah, it's colourful since it was intended to be an all Time Stones boss (good future only). Time flows freely, and Eggman's machine is essentially invincible. The idea being Sonic can reach warp speed at any opportunity (instead of getting the warp posts) and must do so to "wind back the clock" to damage the boss. Some parts are running, some areas the screen is locked. I was slightly worried the idea of running to warp might not be self evident (no warp screen, the level and boss would change in real time with some neato effects).
While Whitehead was still pitching the game's digital port, Simon "Stealth" Thomleynote Known for Sonic Megamix and his famous Sonic 1 GBA proof of concept.began work on a port for theNintendo DS, but the project was abandoned once Whitehead's pitch was accepted.
One of the pieces of concept art for the final boss shows Eggman in a mech suit, though with the panels from the final design still present. This concept eventually became the basis for the final boss of Sonic Mania, the Phantom Egg.