Knuckles in Emerald Coast (Both Acts)

[Zanok the Hedgehog]

It's no secret that it's possible to get characters into acts they were never meant to be in while playing Sonic Adventure, but one stage in particular - Emerald Coast - has always been rather broken while doing this due to how few characters have proper starting points on it. 

Let's fix that. 

The video:

Sonic Adventure - Knuckles the Echidna in Emerald Coast (Both Acts)

 

[Blue Blood]

This is about 19 years old. There's nothing really to discuss here. As you mention in your video description, completing Emerald Coast sends Knuckles to the Mystic Ruins Past rather than Station Square. The area will lack any triggers to further the story, so you end up stuck in there forever and your save file is now broken. The game gets confused about where Knuckles should be sent after finishing Emerald Coast, so it pulls up the level ID for the Mystic Ruins past but the corresponding sequence-specific object layout isn't loaded. Ergo no cutscenes, no progress. 

Are you interested in a bit of background? The thing about SA1, is that when a character doesn't have a level layout file, it defaults to opening "SET**$$?", where the ** accounts for the level ID,  the $$ for the segment ID and the ? standing for the character ID (SET0100S would be the first part of Emerald Coast for Sonic, for example). Modifying or glitching the game in any way to get Knuckles, Tails or Amy into Emerald Coast will load Sonic's layout as a result. And to that same effect, Hedgehog Hammer, Big's Emerald Coast, Knuckles' Red Mountain and Hot Shelter will be devoid of any objects for characters not meant to go to those stages because there's no Sonic layout for them (Knuckles' Red Mountain and Big's Emerald Coast are actually totally unique levels despite how it might initially look). 

The other thing that happens is that every character has designated spawn spot for their stages, and that's stored separately from the object layouts. If a character doesn't have a spawn location because they're not meant to go to a specific level, it just plops them at coordinates 0,0,0. In the first part of Emerald Coast, 0,0,0 is almost exactly where Sonic and Gamma start the level, so you won't easily notice that the position of Knuckles is off. When you reach the next segment as Knuckles in your video, he spawns under the level because that's where 0,0,0 is, and there just so happens to be a spring in that exact location (likely a leftover from testing). When Tails goes to the same level, he's warped back to Station Square as though he'd completed the level. I think this is due to the fact that Tails technically does visit that stage in a cutscene, and the level is set to end the moment that gameplay starts there. 

You can modify the game to create object layouts for each character simply by copying an existing object layout file and changing the final character to S, T (or M, I don't remember), K, A, E or B as required for each character. Using the same example as above, if you create a file called SET0100K, the game will load that for Knuckles in Emerald Coast. Using this you can modify a new layout for the level entirely independent of Sonic's own layout. There exist some really good tools these days for creating and modifying layouts. 

[dbzfan7]

If you have the PC version you can just get the character swap mod which let's you play as anyone of the 6 in any level without having to do workarounds. Though in some cases you do have to switch to the proper character in some sequences.