Screenshots of early concepts of the Saturn version of the game.
The game went through a lot of changes especially going from one console to another.Examples
- As the page image can attest, Sonic Adventure was originally in development for the Sega Saturn, with the Sonic World featured in Sonic Jam serving as a prototype. As such, there are some elements from Jam that can be found in Adventure such as some of Sonic's animations
and an unused spring that can be found via hacking. - Early◊ story◊boards◊ show◊ that◊ the game's intro (specifically Sonic's intro) was much different. It also shows that the game's story was going to have more comedic elements.
- Those same storyboards also shows that Chaos originally had vertical slit pupils in his eyes. These almost didn't make it to his design in the main game—Chaos's forms are nearly all blank-eyed, but Perfect Chaos regains the vertical slits.
- According to some Dummied Out voice clips from Tikal, Super Sonic was going to be playable in the same manner as the Genesis games (collecting 50 rings will let you transform during a level) The idea was scrapped due to the game's level design not being able to adapt to Super Sonic's speed and controls. Although it's possible that Metal Sonic skin uses the unused code for it.
- The in-game engine appearance of Perfect Chaos was supposed to match how he looked in the game's FMV intro and the mural found in the Lost World level, but graphical limitations prevented this from happening. When the fight was remade for the 20th anniversary game Sonic Generations, he was given the intended design since technology had improved enough to allow for it.
- Speaking of Chaos, the final boss was drastically different having Super Sonic travel on top of a barrier and attacking the tentacles to break through the base to defeat Chaos. The idea was simplified in the final to running at great speed in a straight line to attack him. This idea for a final boss was reused for Sonic Unleashed.
- It would appear that early on in development, the characters (or at least Sonic) would've retained the designs they had in the Genesis games. If one looks closely during Sky Chase in the Dreamcast version, Sonic's model resembles his classic designnote . The Sonic pinball table in Casinopolis uses the characters' classic designs. Then there's this tutorial image from the Dreamcast version's website◊ and an old storyboard for the intro uses his classic design. According to Yuji Naka and Yuji Uekawa, Sonic's redesign came from both a desire to make Sonic less cutesy and to restore the original "bad boy" image that he lost over time, as well as finding it to be a necessity to make the design work in 3D as they felt the original design didn't work well in a 3D space during testing.
- A very early Dreamcast prototype, called the "AutoDemo", has been unearthed and searched through. 3 test maps and many early maps were found, but the biggest find was the map geometry of the early Windy Valley, as seen in the game's earliest promotional materials and in the intro cutscene. The map, along with structures in the test maps, suggested that the game would have been more dependent on Sonic's momentum, rather than his raw speed, and may have featured physics similar to the Genesis games. Other differences is the level being much more vibrant, with a lesser emphasis on realism, and having a significantly more expansive layout that had many more alternate paths and took longer to clear. This might explain why the final level's Mission A clear time is so forgiving, having been adjusted for the original incarnation. Word of God is that the original Windy Valley was scrapped because it needed a lot of polish (likely due to the final game's physics being unsuitable for it), but time constraints forced them to make a new, simplified version from scratch instead.
- Most of the characters had different animations reflective of their unused abilities.
- One example is Knuckles. He at one point had more combat-heavy abilities such as uppercuts and takedown punches which were seen in the earlier promotional videos of the game. This was possibly scrapped due to its redundancy seeing how most enemies die in one hit anyway. Animations for them can be found in the demo.
- One example is Knuckles. He at one point had more combat-heavy abilities such as uppercuts and takedown punches which were seen in the earlier promotional videos of the game. This was possibly scrapped due to its redundancy seeing how most enemies die in one hit anyway. Animations for them can be found in the demo
- Sonic's Light Speed Attack works differently in the demo and is the only upgrade implemented in the demo. Sonic kneels down instead of rolling and the player can press A to move or B to turn the move into a standard homing attack.
- Data inside the final game refers to unused levels such as a desert, jungle, and mushroom stage.
- There was a promotional image of Sky Chase with a fire-breathing mechanical dragon boss, but it's not present in the final product. It actually still exists within some versions of the game, but when hacked in all it does is follow the player without attacking, it lacks proper animations, and nothing happens if you shoot it.
- In one demo of the game, using a cheating device to access the Chao Garden reveals a different Chao releasing mechanism. Simply put, it's a button that, when pressed while a Chao is placed in front of it, a grate opens up, it falls into it, and grinding and shredding sounds are heard. These sounds were possibly meant to replicate the Dreamcast processing noise and for the Dreamcast VMU device but seeing that the demo was not programmed for this feature, the screen on the mechanism says no data and there is no way to get the Chao back.
- Knuckles' voice in the E3 1999 demo was different from the version in the final product. He had the same voice actor, however the voice direction was very different and more serious sounding. The lines were also slightly different. One of his lines ("Oh no!") was used in the final product, however in a separate cutscene. Oddly enough, some of these voices actually ended up used in Sonic Adventure DX, but only the ones that played outside of cutscenes.
- The game was planned to have a kids meal tie-in from Burger King featuring ten different toys, set for a release on December 10, 1998. Most likely due to Sonic Team delaying the American version of the game to patch up the glitches in the original Japanese version, this promotion was scrapped.
- Shortly after Sonic Team decided to redesign Sonic, there was a competition held between some of Sonic Team's artists on how Sonic should be redesigned, the top 4 submissions for Sonic's redesign, showing different designs of him, were showcased in the Japanese magazine, Sega Harmony, which can be seen here.note Yuji Uekawa's design ultimately won and would become the basis for Sonic's Modern redesign.
- Going by concept art, Hidden Palace was originally going to be in the game, seemingly accessible through a secret entrance at the feet of a huge echidna statue. Interestingly, the Emerald Altar there was depicted as being within a large pillar structure per the Japanese manuals of Sonic 3 and Knuckles Chaotix, and still contained the Master and Chaos Emeralds, implying they had remained there since being returned in Sonic 3 & Knuckles. In the final game, the Chaos Emeralds are scattered all over the land, and the Master Emerald was relocated to an outdoor altar. Curiously, when the concept art was revealed on social media, it was attributed to Lost World. If this is accurate, it would imply that Hidden Palace was reworked into Lost World at some point (likely when it was decided to implement the outdoor altar), explaining similarities between the two areas such as presence of the legendary dragon/Perfect Chaos mural (implied by the Japanese Sonic 3 manual to be in Hidden Palace).
- A screen of the original incarnation of Windy Valley was used to promote Sonic Adventure DX, implying that this one was originally going to bring back scrapped content intended for the original Dreamcast version. This might explain the extraneous Director's Cut subtitle.
- In 2020, Satoshi Okano, a former Sonic Jam artist and field artist for Adventure, revealed on Twitter that the bikini-wearing character seen in posters of Speed Highway was a planned character who ultimately went unused. Three years later, he revealed a full-body concept sketch of "Spider-Girl." This would possibly later become Rouge the Bat (based on Spider-Girl's heart motif).
