Sonic & Knuckes & Knuckles & Knuckles

Sonic & Knuckles was a marvel to the youth of the 90s. It was a Sega Genesis cartridge with seemingly magical powers. It had a slot at the top, which meant you could stick other games in there – when you put in Sonic 2, Knuckles would be playable in that game, which was released almost two years before.  If you put in Sonic 3, you got the “full” Sonic 3 & Knuckles experience, a long, contiguous series of sharply designed Sonic levels. If you put in any other Genesis cartridge, you got an instance of Sonic & Knuckles’ special stage that was unique to that cartridge. Put in Sonic 1, and you get a whole slew of specially designed special stages. To a young child, what else could that be but magic?

Of course, the Sonic 3 & Knuckles connection was long planned. The Sonic 2 connection still impresses me – one game is basically hacking into the other. But there was always one kid on the schoolyard who claimed the magic didn’t stop there – her cousin had three copies of the game, and if you stacked them all… something happened. Most of us couldn’t afford one copy, let alone three, so back in the 90s, we didn’t have much occasion to check the validity of this theory.


Round about two years ago, I was in Austin, Texas to show our game Gunsport at the Rooster Teeth Expo. I was staying with then-labelmates Eric and Kat Wenske, makers of Capsule Force. I don’t remember how it came up, but Eric started talking about how, in his youthful summer days, he and his friends would combine their collective pool of sonic and knuckles carts, stacking them to see if they’d still work. They did this every summer, and as time wore on, the carts got cheap, and the stack grew. At some point, he inherited all 12 of them. In fact, they were in his closet.

Had he ever tried to stack them all? “No,” he said. Should we… do that right now? “Heck yes,” he said. And so we did. And I can tell you, the magic never dies.


We stuck with a specific methodology. Essentially, if you stack a bunch of Sonic & Knuckles carts by themselves, you can’t really know what’s happening, or how far up the chain you’re getting. If it’s all the same game, the title screen will just show Sonic & Knuckles, regardless of whether it’s registering the cart at the top of the stack, or only the bottom one (or the middle, why the heck not). Given the propensity for cartridges to not register due to dirt or corrosion at the best of times, we needed to be sure it was going all the way up.

If you have a Sonic 3 cart at the top, you’ll know what you’re getting. If the title screen says Sonic 3 & Knuckles, you’re getting the full run of carts. If it says Sonic & Knuckles only, you’re missing something along the way.

Normal Sonic 3 & Knuckles title screen

Normal Sonic 3 & Knuckles title screen

Normal Sonic & Knuckles title screen

Normal Sonic & Knuckles title screen

We started out with two Sonic & Knuckles carts, and worked our way up to 12 total Sonic & Knuckles carts plus one Sonic 3 on top. Some day, maybe, we’ll push it a little further. I took vines of the whole experience, and I’ll commentate them as we go along.

3 carts:

This was our initial try. Honestly I wasn’t expecting much from this whole experience, yet. I really didn’t know what to think about this whole thing!

6 carts:

There were no changes between one and five Sonic & Knuckles carts, but once we got to five, we started to notice some differences. This was subtle, but the white flash between Sonic dashing at the screen and the title was noticeably longer.

8 carts:

So here we had that problem I mentioned above. We couldn’t tell how far up the chain we were getting, because the screen just showed Sonic & Knuckles. We took them all out and cleaned them, and tried again.

8 carts, human interference:

But first! As we were about to take the carts out to clean them, we noticed that jiggling them at all caused everything to glitch out. It’s not surprising, but it’s interesting to look at regardless. For science!

8 carts, again:

Now we’re getting something. 8 carts, registering all the way up, and we see visual glitches and an oddly flashing title screen. Now I was convinced we were on to something with this experiment.

8 carts, protip:

As you can imagine, when you’re stacking up all those carts, they start to lean. It’s nearly impossible to keep them straight, they’re like a wobbly worm on a hook. Through trial and error, we discovered that leaning them toward the back of the console, rather than toward the front, would give us a higher chance of the signal getting through. The other way, well, you can see how well that works above.

9 carts:

Yep, it’s getting weird now. A lot of sprites are showing up as lines and boxes, including poor Tails on his little airplane back there.

9 carts, trying to get in to the game:

Before now, we didn’t get much in the way of gameplay difference, it was just the title screen that was odd. Starting with the next one, you’ll see that the menus in-game are pretty messed up too. But when you’ve not got the connection quite right, even if you see the title screen, you’ll get this screen when you press start. This is what shows up when you put something into the S&K cart that’s not supposed to be there, or which the game doesn’t recognize. Instead of giving you a special stage, it gives you this “no way!” screen.

10 carts:

The in-game menus are messed up as heck, but we know this game well, so we navigate to start. It… tries to start, but freezes on the opening cutscene.

10 carts, on the frozen screen:

We stayed on that screen, trying to make something happen, and it appeared as though the music was playing at something like 10x speed, and then got stuck on one note. It was pretty surreal.

11 carts:

Oddly, with 11 carts, while the Sega logo had lots of odd artifacts around it, the title screen looked better. Was this due to human error? This isn’t an exact science here, so my answer to your query is “heck if I know.”

11 carts:

We got into the game with minimal problems. We had gotten better at holding it up – Kat was contorting herself to make sure there was an optimal connection, which was very helpful. In this vine, you’ll see that Tails has some stray pixels floating around, making it look like he’s got fleas.

11 carts, special stage:

Oddly, these “fleas” carried over to the special stage, even though it’s a totally different sprite used. Just around poor Tails.

11 carts, supersonic:

Supersonic actually held up pretty well, but the rocks didn’t fare as nicely.

12 carts:

Lol 420

12 carts, title screen:

This is the stuff you paid to see! What a wackiness. All kinds of glitches and things I didn’t expect – I always assumed Sonics head was part of the surrounding ring, but it looks like they’re glitching separately?

12 carts, getting into the game:

Characters flicker  in and out, everything’s green (lol 420), the special stage is a total mess, but you can play it still!

12 carts, special stage:

We got pretty fixated on the special stage. Floating orbs! Half the screen is blue! Collision is unpredictable! I’d live there.

12 carts, level select:

We decided to input the level select code. Here’s what that looks like, as well as the second bonus stage!

13 carts, no Sonic 3:

Sonic 3 wasn’t registering again, but we still got some fun glitches at this point, so it must’ve been getting through to a whole bunch of those S&K carts. We cleaned everything again.

13 carts, SOS!!

At this point the game cries out for help. What has science done!?! I am so sorry, Sonic!

13 carts, doesn’t want to work:

We could get the title screen to show up, but it was real tough to get past hitting start. It really wanted to give up the ghost and just reset.

We (by which I mean Kat) tried many contortionist positions to get it to work. This one was impressive, but… it did not work. What actually worked was when she was standing next to it, holding it close to her leg. Kat is pretty short, so at one point she was kind of just hugging the stack.

13 carts, in game finally:

In the end, we got it to work. Total mess. It’s great! Sonic is a true hero.

13 carts, can’t pass the demo:

The Vine cuts off a bit too early, but trust me – as soon as the cutscene ends, you hear the sonic death sound, and it starts over.

13 carts, we did it!

Somehow we got past the instant death, I think we had to hold left constantly or something?? There were some hidden spikes somewhere that we had to avoid. But there’s all sorts of collision that shouldn’t be there, so we couldn’t move much.

13 carts, same old problems:

We tried to get around all that biz by jumping, but found ourselves in an even deeper hole with less mobility.

13 carts, competitive mode:

Why the heck not try this too, eh? It basically works!

13 carts, NO FACE:

Who would have predicted Knuckles’ face was a separate sprite? Well, it’s gone now. The horror!

13 carts, level select:

Sonic Pole Riders! In the level select, Sonic is doing the animation for when he’s holding on to a pole in the underwater sections. The game is really giving up the ghost.

13 carts, back in the box:

Yep. There we are, stuck again. SIGH. Unfortunately we couldn’t get the level select to work, to try to bypass the levels we couldn’t get through.

13 carts, spin forever:

But at least we discovered something! Turns out with 13 carts, you can spin up almost infinitely! (That’s not the natural sound, right there!)

13 carts, plus Sonic 1:

As I mentioned, this will get you a bunch of special stages. We decided to try them out. So… is it Sonic One, or Sonic Two? (Because there are two Sonics, do you get my joke, please get my joke.)

13 carts, Sonic 1, as Knuckles:

Pretty much more of the same, but with two Knuckles this time! At this point we pretty much went off to bed, all that Sonic glitching takes a lot out of you. We went and bought a couple more Sonic & Knuckles carts the next day, but weren’t able to put them to use, because:

The cables went bad:

Yeah. Here’s what happened when we tried to play again. Totally different glitch. This one’s a bit unfocused camera-wise, but:

This one’s a bit better:

At least this is enough to prove that everything we saw previously wasn’t the cable’s fault. Still a fun effect!


Because of the cable, and our own excitement, this experiment ended before it should have. We didn’t try the game with Sonic 2 – would Knuckles get all wacky in that game? Would it even work? In the future, I’d also love to try this with the Korean Sonic 3-in-1:

Or Sonic 3D Blast (which can glitch out just fine on its own, thank you very much):

So what’s going on with all the Sonic & Knuckles magic? Our best guess was that the game is looking for data in certain parts of the ROM, and each subsequent cart shifts over that location by a very small amount, causing the game to bring up parts of the spritesheet, music, sound, etc that aren’t meant to be loaded then and there.

But this is total armchair theory, and I could theoretically go out there and ask a real person and get the real answer. But do I want to spoil this for myself, and for all of us? Isn’t it better, perhaps, just to believe in magic?