Wouldn't be an issue if SEGA had some sort of archive of their own assets that licensed devs would have to pull from if they were not making their own. Stuff like Sonic Speed Simulator definitely has to rely on asset rips from Models and Textures resource - their animal capsule model (when they had one) was a rip from the Statue Room in Sonic Generations and nobody thought to remove the base stand. As far as the issue itself goes, not everyone can have intimate knowledge or time to double-check whether something that looks official (many things do) actually is. I can't imagine scrolling 10 pages of results on Google trying to find official sources because you're given a "Good luck!" from the people who would normally provide those resources is a really good use of work time either. Even someone you'd expect NOT to fall victim to these issues - the guy working on the Sonic 3 Origins sprites - did.
Here is a video of Jason Griffith using his Sonic and Shadow voices to say sentences I would never imagine an official Sonic voice actor would say in their Sonic and Shadow voices
EDIT: Nevermind! Keep an eye on any Sonic X-treme related pages in the coming weeks, we're going to be a documenting a ton more
I was digging through the Models Resource page on the Wii version of Sonic Colors and found something interesting: it features at least two unused spring variants, both of which also appear in Unleashed. Spoiler: Spring #1 Spring #1 is a blue spring and jump panel, which all of us should recognize as appearing in many levels in Unleashed to trigger QTEs. Colors gets rid of the Unleashed-style QTEs, but this suggests they might've been planned at some point. I can think of three possible places they'd be used: The scripted wall jump sequence towards the beginning of Starlight Carnival Act 1 To bridge the gap between Planet Wisp Acts 1 and 4 when they were originally one long level, ahead of being split The space areas in Asteroid Coaster where you have to use the homing attack on springs on asteroids rather than break the asteroids Spoiler: Spring #2 Spring #2 is the thorn spring, also known as that really fucking annoying spring with spikes from Jungle Joyride in Unleashed. This is the one where I have absolutely no theories as to where it could've been used.
I don't think they're there because they were planned to be used. They're probably left-overs due to Sonic Colours using the same engine as Sonic Unleashed Wii.
Colors doesn't use the Unleashed SD engine. It's seemingly based on the Secret Rings/Black Knight codebase, as the layout format, scripting files, and physics engine are the same, and it shared a good chunk of staff (including Kishimoto as lead designer/director). I don't think it shares any code with the Wii version of Unleashed, which was made by a separate team - and I don't believe the thorn springs appear in the SD version at all (but they DO appear in Secret Rings!).
Of all things to change, Sonic & Knuckles Collection features a completely different palette for the Glowing Spheres Bonus Stage. The original game features a palette that cycles through the different colors of the rainbow, whereas the PC version instead opts for a hot pink/purple/blue palette cycle.
This is the result of a bug and you can take a guess why this is happening just looking at the screenshots: the game is applying the rotating palette used for the spheres to the background EDIT: I take this back slightly; the game is certainly applying a wrong palette but it's also applying the same wrong palette to the spheres. I'm not sure where the palette they are using comes from
I had a hunch from the moment I read this, and it's correct: the game is reading the palette with the wrong byte order, and as a result red and blue are swapped and green is discarded. The reason this happens is because this is a rare instance (possibly the only one) of the game storing an animated palette in a compressed format, and the people who made the PC port did not redo the file to swap the byte order (it's identical to the MD version), nor did they perform a swap at runtime. It's extremely easy to fix, like most of the issues with the port. Thanks for pointing it out to me! Edit: and here's a mod to fix it!