Press the Jump button twice as if you were to perform that character's 2nd jump move (i.e.: Sonic's "shield dash"; Tails' starting to go into helicopter mode; or Knuckles when he's about to start gliding).

It always has been that way, and if I went bothering seeing the Sonic Origins' Manual[manuals.sega.com] or its *.pdf file almost 100% assuredly that it'll tell you the very same thing as I did above.

Edit add note: Apparently upon the PC remake of this game there are now special keys that need to be pressed[manuals.sega.com] even when having 50 rings and possessing either the Chaos Emeralds and/or the Hyper Emeralds.
I stand corrected and it makes much more sense because when I was playing this upon Sega's MegaDrive/Genesis console I don't recall us having that option apart being extra careful to only activate that jump when needed.

How stupid is that? Special key combinations. Just press jump twice and done like old times on the megadrive when i played sonic. I will try the combinations

I've linked you the specific page upon the Sonc Origins Manual upon my Edit add note. It's a simple one if not mistaken after teking the jump, but I didn't tried it.

To be bluntly frank, I've never tried it because never played much Sonic Origins upon the PC although got it for sentimental value upon my teens both the Sonic 3 and Sonic & Knuckles cartridges connected being, imho the best, and also my favorite Sonic game of the whole starting 3.
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It also was funny to also try to circunvent the less jumping height of Knuckles to progress through levels while attaching the Sonic & Knuckles cartridge to a friend's Sonic 2 one and having that extra added difficulty amount of fun when for ex. facing the latest Robotnick's Mecha boss upon that Space Station's last level.

I tried yesterday to jump and press o on keyboard and it workt. Sonic turned into super sonic. Now the game is much easier than before 😁

I imagine this is a bug that's been fixed for this re-release, but be warned that in the original Sonic 2, if you jumped to turn in to super sonic after hitting an end-zone post but before you ran off screen, sonic would attempt to transform, be unable to, then be stuck running in mid-air. Because zones won't end until sonic has ran off the side of the screen, it would become soft-locked.

I'd like to imagine this is a classic bug that has been fixed though, since I noticed when playing through Sonic 1 that they've made a lot of tiny adjustments in some spots to fix a few errors... though the altered hit boxes constantly kept catching me out.

Originally posted by Chefry:

How stupid is that? Special key combinations. Just press jump twice and done like old times on the megadrive when i played sonic. I will try the combinations

i believe its to have consistency with sonic mania , most likely also to allow you to fly as tails or glide as knuckles if you dont want to become super yet

I'm having the same problem. So then how do you transform into Super Sonic then on PC? You have to press O on the keyboard after jumping?

press K on keyboard to jump and when in air press o (not zero) to turn into super sonic. But if only works when you have all 7 chaos emeralds and 50 rings

Originally posted by Chefry:

How stupid is that? Special key combinations. Just press jump twice and done like old times on the megadrive when i played sonic. I will try the combinations

I prefer it this way because then I can choose between using other jump actions, like shield powers or having tails lift me up, without having to cash in my rings yet

Press the top face button on your controller:

"Y" for Xbox 360, Xbox One, Xbox Series, Steam, and generic controllers,
"🔼" for left Joy Con on its side, "Y" for right Joy Con on its side,
"X" for two Joy Con or Nintendo Switch Pro Controller,
"△" for DualShock 4 and DualSense controllers,
"O" key for keyboard (though if you prefer WASD and mouse as opposed to WASD and KLIO, you can map it to also be on Mouse Button 3 [Scroll-click as I call it], or Mouse Button 4/5 if your mouse has extra buttons)

This is a carryover from newer games, specifically Sonic Mania's v1.03.0919 update. In Sonic the original Mega Drive / Genesis version of Sonic 2, you'd be forced to transform after getting 50 rings on your next jump. In Sonic 3 (& Knuckles), you have to press the jump button twice to transform, which was carried into Sonic 1 (2013), Sonic 2 (2013), and Sonic Mania, though you would have to lose your elemental shield first if you wanted to transform. In v1.03.0919 of Sonic Mania, it was updated to add a dedicated transformation button akin to Sonic Colors, Sonic Generations, and both episodes of Sonic 4, being mapped to the buttons above, except for keyboard being on "W" instead of "O" due to being controlled with the arrow keys and jumping with ASD.

This is a QoL improvement made so that you do not have to intentionally lose your thunder, lightning, or bubble shield to transform, and so you can use your jump abilities (flying with Tails, gliding with Knuckles, Hammer Spin as Amy, and Insta-Shield and Drop Dash as Sonic) without transforming.

I didn't want to start yet another topic on this subject, but I have small question about activating Super Sonic:

I recently finished the story mode and managed to get all seven chaos emeralds in the during the Sonic 3 and Knuckles part. I managed to get six of them during the Sonic 3 levels and the last one in Mushroom Hill, but super sonic would never activate no matter what I did. Did I have to get all seven regular emeralds during the Sonic 3 levels to get super sonic? If that's true, I assume you have to get seven super emeralds during the S&K levels to get super sonic in that half of the game?

Originally posted by Giant Wasp Face:

I didn't want to start yet another topic on this subject, but I have small question about activating Super Sonic:

I recently finished the story mode and managed to get all seven chaos emeralds in the during the Sonic 3 and Knuckles part. I managed to get six of them during the Sonic 3 levels and the last one in Mushroom Hill, but super sonic would never activate no matter what I did. Did I have to get all seven regular emeralds during the Sonic 3 levels to get super sonic? If that's true, I assume you have to get seven super emeralds during the S&K levels to get super sonic in that half of the game?

Yeah.
Once in Mushroom Hill, you're aiming for the Super Emeralds and Hyper Sonic.
You get a cutscene showing the 7 regular Emeralds plugging into the giant Super Emeralds to show the goals have changed.