What were your headcanons, as kids?

[Kellan]

I was under the impression that E-102 Gamma was saved by Sonic and friends after his heroic sacrifice. They took him in, gave him repairs, and gave him a new power source so that he wouldn’t need to be flicky-powered anymore. Now powered by the Green Chaos Emerald, this is how we got E-123 Omega.

Note that this theory doesn’t say why he suddenly looks different and has a different name. That’s because kid me didn’t even notice that these characters don’t share a name, or appearance. I just thought it was the same bot, completely unchanged.

[Splash the Otter]

The first time I saw Shadow, I thought he was an alternate form of Sonic.

[Iko]

I was very young, can't remember my age, though, I was convinced that Sonic's goal was to collect rings and emeralds for his girlfriend or wife; at the time I didn't know Amy existed, and when I realized Amy was a thing, I thought the theory was legit (it was before the modern era existed); I thought that Robotnik (that was the only name I knew at time) was just a side character that you fight for the sake of it, but the main plot of the game was just Sonic collecting jewels for his girl. That was not completely my fault, it was because of my brother saying that he read so on a magazine or something, and considering all the stupid inaccurate stuff that was possible to find on some media at the time, I won't exclude that he may have read it for real.

When I played 3D Blast (Genesis/Megadrive) for the first time, when I found Knuckles, I didn't recognize him (can't remember if because I didn't know him at all or if because the sprite was unclear and I was confused), and I thought it was a new character, and a girl. I completely forgot about that, but may years later, when I played Sonic Rush and I saw Blaze, I had a flashback, because the way I imagined that character, was extremely similar to Blaze, and I remembered it because of her.

This is not misconception, this is just headcanon, I was aware it was not canon and was just a theory of mine: I liked to think that there was some mysterious character helping Sonic from the background without ever showing himself, putting monitors and rings on his way before he arrived. I even made an OC out of it, my only OC in my entire life (excluding the Avatars in Sonic Forces); I was a teenager at the time.

[Big Panda]

This was a lot later into my childhood (I was about 11 or 12), but when I was first introduced to Archie Sonic, I was so into it that I believed it was *the* main Sonic canon, and that the games, SatAM, AoStH and even Sonic X were canon to it (I used to imagine the events of Sonic X's Adventure adaptations were somehow happening in relation to the comics' own adaptations somehow. Yes, I know that makes no sense at all).

Of course, Underground was established as an AU in the comic, so I accepted that. And I'd just more or less forgotten about StC by then...

[Nicky Nicardo]

I dunno if this counts as a headcannon or not, but... when I was a kid, and was first dabbling in fanfiction after playing/seeing my sibling play Sonic Adventure 2, I gave Tikal a brother. Who was basically Knuckles colored peach and wearing pants. And he had to rescue Tikal from Eggman. And I thought he was just too damn cool.

Good times. Cringey, ridiculous good times. xDD

[A person, that exists]

I thought that Doctor Eggman was actually a robot and that the Eggrobo from Sonic&Knuckles was actually just his "True form". 

Also, speaking about S&K, while this is not a headcannon, but I couldn't pronounce the word "Knuckles" back when I first played the game, cos I didn't know English all that well, so I always said "Nookles" or "Knakles" instead. I also thought that he was a girl, and a fox, thanks to these awful bootleg Russian box covers and manuals.

Heck, I even remember drawing some weird comics, where "Nookles" would be a total jerk to Sonic, but would also fear Robotnik, because he was kinda her superior. 

Also, I didn't know that Tails was a real character, and thought that he was just a phony character that my friends made up. And who could blame me: a fox that could fly sounded like one of those "Press A, B, C and the power button to play as Ken from Street Fighter in Mortal Kombat 3" cheats. 

And when I found out that Tails was real... Well... This is where I began to ship him with "Nookles", cos they were both foxes and all. Heck, I even thought that Tikal was their daughter when I first saw her on the cover of a bootleg SADX disc. 

And then, when Sonic X and Underground began airing on Jetix I was like "What? Nookles is a guy? Who is Shadow?". Like, it cleared a lot of things, but I was still confused, kinda. And speaking of X, I thought that SADX, Riders, SA2, Heroes and Shadow the Hedgehog were all based on seasons/episodes of the show.

And speaking of Heroes, I always thought that Metal Sonic and Eggman were the same entity, because I didn't have the balls to beat Chaotix' story, and that Omega is in fact the original Robotnik/EggRobo, that was overthrown by his own creation all the way back in S&K, when Metal Sonic destroyed his EggMobile while fighting Knuckles.

[BaronGrackle]

33 minutes ago, A person, that exists said:

and that Omega is in fact the original Robotnik/EggRobo, that was overthrown by his own creation all the way back in S&K, when Metal Sonic destroyed his EggMobile while fighting Knuckles.

I think we can still think of them as the same "family tree", since Omega was inspired by Gamma and Gamma's early designs show he was influenced by Eggrobo. (humanoid badnik with a gun)

[Harkofthewaa]

As a 4-year old kid, my parents had a Sega CD along with Sonic CD, and obviously I played the crap out of it. However, the Genesis broke (revealed many years later after digging it up to be a bad power cable, something easily replaced ) Anyways, over the years bad memory set in, and with my family not getting Internet until I was a teenager, for the longest time I "remembered" the following about Sonic CD:

A.) That in the intro, the Little Planet was set over a forest instead of a lake. The fault of my bad memory somehow confusing that border for trees.

B.) That the Special Stages were trippy (so far correct), and you ran around in a maze to get to the exit (wrong).

C.) I misremembered some of the colors of levels; I thought Collision Chaos had a bright blue sky, and that the first boss in Palmtree Panic had a bunch of pink pipes set behind it, along with an orange sky.  

Needless to say, when I finally managed to play Sonic CD again (First through the Games Collection on the Gamecube, then the Taxman version on 360, then the original version that had been sitting in the attic for 10+ years. Yeah, I went on a quest.) I really had a laugh.