Sonic & Knuckles + Sonic the Hedgehog 3. If you grew up with this combination you already know that I'm talking about one of the best games ever created. The two were originally meant to be one really long game, but because of cartridge limitations and demand for a new Sonic game, half of the game was released as Sonic 3, the other half was released as Sonic & Knuckles. This was a win for both game players and Sega. We got the blue sphere mini-game, and Sega got to profit off of two games instead of one. But we're not here to discuss the history of this masterpiece.
So we all know about the secret Blue Spheres minigame. We also know that there are two versions of it. Locking on Sonic 1 gives us the first screenshot: everything is well lit, a "Level" indicator is present, a "Start" option, and most importantly a "Code" section. Sonic 1 is the only game that allows you to enter a code to revisit an old stage. The second screenshot is usually what happens when you plug in a cartridge that is not Sonic 1, Sonic 2, or Sonic 3. You get a single bonus stage, which upon completion will give you a code. This code can be entered into the Sonic 1 code section to allow you to revisit this level! And what's really neat, is that the characters will even turn dark after it's entered.
Today we know there are a total of 134,217,728 stages when locking on Sonic 1 before it repeats. This is a finite number. We also know there are slightly over 900 games created for the Genesis, this is also a finite number. Let's assume that 900 is the total amount, adding that to the Sonic 1 stages means a maximum of 134,218,628 stages exist. Well I'm here to say there can be more! And it's because of a cartridge glitch I discovered when I was really young by accident that I know that this is possible. After over 20 years, I'm finally sharing this so the knowledge doesn't eventually die with me.
So let's go back in time to the 90's, I was really young (about 10) and pizza was still a relatively new and wonderful thing. Sega Genesis and the Super Nintendo were the top consoles out, and Mario and Sonic were still taking their place in history. I remember being at the mall with my grandparents around Christmas time, and I saw Sonic & Knuckles sitting on the shelf. I begged for it, I wanted it more than anything. I didn't have Sonic 3 yet, but still, there it was, sitting on the shelf just out of reach. They eventually gave in, and I thought OMG it's mine! It wasn't until months later that I got to play the full game with Sonic 3, but it's also fortunate because this glitch was discovered due to that fact.
So getting back on track here, Sonic & Knuckles never left our Genesis for weeks. One of us must have dropped a piece of pizza into our box of Genesis cartridges, because some of them were covered in hard dried up cheese and other grime. But hey, we were kids! One day we decided to lock on Sonic the Hedgehog 2 because it brings Knuckles into the game. When we first locked it on, we were instead brought to the dark blue "NO WAY" screen. WHAT? WHY? Knuckles you're supposed to be a playable character!
Turns out that some of the cartridge pins had dried cheese on them, which caused the Genesis to think that this is a game, but it's not a Sonic game! This has the interesting property of generating a completely new "Blue Sphere" stage that would otherwise not exist!
Now this goes a bit deeper because we know that each game give us only "1" bonus stage. By blocking some of the cartridge pins, the game can become unstable and start generating stages at random. Here are some patterns I noticed:
- Sometimes you only get a single new stage.
- Sometimes you get unlimited stages that don't vary much.
- Sometimes it cycles between 2-4 stages, with almost none to extreme differences.
- Sometimes you will get a stage, and the next stage will be different but it won't change again.
There is a caveat. If you complete a stage when it's cycling stages, then you will get the code for the "next" stage. Meaning you can never get the code from the stage that you are currently trying to complete.
Now keep in mind this does not work for all Genesis cartridges. Most of the time, it will fail to detect a locked on cartridge and just boot into Sonic & Knuckles. Sonic 2 was a really easy game to flake out and get the NO WAY screen. The only other game that I can remember getting more than 1 stage from is X-MEN, but I do know that there were others as well. Sonic 2 alone probably gave me over 30 unique stages that would not have existed without this glitch.
It's really easy to try this at home, all it takes is a small piece of paper. Wrap it in a way that it covers some of the cartridge pins, plug it into Sonic & Knuckles, and take it for a spin. If it doesn't work, try moving the paper around. Sonic 2 is a really good game to try this out, somewhere near the center is where you can find a ton of bonus stages, and again somewhere along the edges. I used to even go as far as trying multiple pieces of paper and getting even more stages!
So that's the Blue Sphere/cartridge glitch of Sonic & Knuckles. I don't know if this is known anywhere else because I've never found a single reference to it. I doubt that it has any partical use, as there are already more stages than anyone would ever be willing to complete in a single lifetime. But, it does prove that there are Blue Sphere stages that can exist outside of the known limitation that can't be found in any other way.