- Sonic 3 & Knuckles has a puzzle appropriately known to fans as the "Barrel of Doom". It's found in Carnival Night Zone Act 2, and it's so infamous that series creator Yuji Naka publicly apologized for it in 2011 and an Urban Legend of Zelda suggests that calling Sega's help line at the time would give you an automated message telling you how to get past it. All it takes is standing on the barrel and alternating between pressing up and down on the D-pad, in sync with the barrel's bobbing motion, to shift its weight. Except nobody could figure it out because:
- You encounter other barrels in the game, every one of which is passable just by jumping on it. They're all even skippable, and this is the only one that isn't (unless you're playing as Knuckles). Jumping on this barrel will move it, just like with all the other ones, and if you jump on it enough, you can theoretically spin-dash under it when it pops back up (but this is really hard to do, and it usually doesn't leave you enough time to finish the level), so players would assume that this is what you have to do — and get frustrated when they almost pull it off, thinking they're on the right track but just not doing well enough. In fact, jumping on the barrel is the only thing that's guaranteed to give instantaneous feedback, and veteran Sonic players are conditioned to expect that feedback to show the way forward.
- While the Down button has a few select uses, primarily the Down+Jump combo to initiate the Spin Dash, the Up button has little to no use elsewhere in the game or in the previous Sonic games. Even pressing it while on the barrel while it's stationary doesn't make it move, so no feedback there. Pressing up or down doesn't even make Sonic look up or duck down like he does elsewhere. The only way you'd figure out that it does do something is by desperately mashing buttons and hoping something happens. And just standing on the barrel causes Sonic to spin around vertically, suggesting that he can't even be controlled unless you jump off it.
- The barrel wasn't even designed to be a puzzle. It was simply one of many obstacles designed to slow you down and eat up your precious time. The developers failed to consider that figuring out how to get past the barrel would even be an issue. This might be why the game's manual mentions Dr. Robotnik's "diabolical traps" that were designed to be inescapable except for letting time run out; while most people thought it referred to the Barrel of Doom, it did so in the context of being one of many things (some of them glitches) that would slow you down, not something that you had to solve. This conception of the Barrel was lampshaded in the Archie comics, where Omega encounters the Barrel and decides to just blow it up.
- Sonic Adventure:
- The first game has a few Adventure Field emblems that can be tricky to find:
- One in the Mystic Ruins requires flying over a large, seemingly empty space as Knuckles — and the emblem itself won't show up because of the draw distance until you're actually close to it, so you wouldn't even think about jumping and gliding across that super large bottomless pit unless you somehow knew the emblem was there.
- One in the Egg Carrier requires you to fly on top of the giant spinning contraption at the back end of the ship's outside area as Tails. However, the emblem is only collectible when the ship is in wings out mode that separates the front and back ends of the ship and allows you to enter the Sky Deck stage. You change the ship around by pressing a big red switch on the ground located in the control room near the giant spinning thing. Every time you come back to the Egg Carrier after it's landed in the sea, the ship is always set to wings in mode by default. It's so obscure that even if you went up there the first time with the ship in wings in mode and found no emblem up there, then you'd likely think that particular emblem was located somewhere else, leaving you stumped until you finally looked up and found you have to transform the ship to make the emblem appear.
- Most of the secret optional powerups and upgrades for all the characters, despite not being explained or shown in the manual, are not that difficult to find if you take time to explore the Adventure Fields (except for one upgrade for Big that is actually found in a secret area of Ice Cap). However Amy's Long Hammer upgrade is the big exception. In order to obtain it, you have to play the Hedgehog Hammer minigame again and get a certain high score. However, you have to do it in the Adventure Field after getting the Warrior Feather (doing it in Trial mode in the Games menu won't work), and you have to do it after the Egg Carrier has landed in the ocean. This requires you to think to go back there either immediately after Tails drops you off in Station Square (by taking the boat) or after killing Zero. Nothing in the game ever hints at giving the Hedgehog Hammer another go after the Egg Carrier crashes, so many would have seen no point in playing the game again other then to get the emblem for it in Trial mode.
- During the final boss fight of Sonic Adventure 2, it's possible to switch characters by flying past the FinalHazard. The game doesn't tell you how to do this, which can be real problematic if you're running out of rings but can't land a hit.
- In general, Amy has an unusual control feel; she's pigeon-toed with an overlapping gait, which causes her to run a lot slower than she would otherwise. The way to get her grade A emblems is by getting her to take the biggest leaps possible as you move through her stages. Nothing in the game tells you anything about this.
- Both Sonic Adventure games feature Chao, cute little critters that you can breed and raise. The games are not very forthcoming with how you go about doing that and what else you can do with them:
- You can only see a Chao's stats, give them a name, and access the different types of fruits — but only if you transferred them into your VMU via the machine located in each garden. Neither game explains this, not even in the manuals. The first game has a monitor in the Station Square garden hinting that different fruits have different effects on each Chao, but it doesn't explain how to obtain them.
- Chao have two invisible stats, Luck and Intelligence. Nothing in either game tells you how to increase these states, or what they do, leaving many gamers baffled. They're important, though — Luck prevents Chao from tripping (useful when racing them), and Intelligence helps them solve puzzles. In the second game, a Chao's Luck and Intelligence stats can only be raised through the VMU — Luck through a minigame, and Intelligence by feeding the Chao a special fruit only obtainable on the VMU. Not only is this not explained to you, but you wouldn't be able to raise these important stats if you didn't have a VMU.
- In the first game, a Tikal hint orb will tell the plays that animals can change a Chao's appearance, but it won't tell you that the also affect a Chao's stats.
- A Chao's stats are randomly determined at birth. If it has an E ranking in a stat you wanted to raise, no matter how much you give it it will raise extremely slowly and weakly, and always be weaker than a Chao with the same level of a higher rank. You can gradually raise the ranks by training them in the weaker stats until they evolve or reincarnate, but the game does not tell you this.
- The first game has a few Adventure Field emblems that can be tricky to find:
- In Sonic Heroes, there is at least one point (Extra Mission for BINGO Highway) with Team Chaotix where you have to use Leaf Swirl to turn Espio invisible so he can pass some lasers. At no point in the game is it mentioned that turning Espio invisible makes him able to pass through lasers.
- Like most Sonic games, Sonic Advance 2's true ending can only be seen if you collect all seven Chaos Emeralds. However, to get to the Special Stage to even attempt to get a Chaos Emerald, you have to collect all seven of the Special Rings hidden in any given level. Unfortunately, as a later Sonic game, it wasn't really known for its exploration, and most players would end up running right past them. It doesn't help that backtracking is pretty much impossible, and players would either have to memorize an entire level to get them or get the game guide with the detailed maps. And you lose the rings you got if you die.
- Shadow the Hedgehog has Space Gadget. The Hero mission is just the Neutral mission on a five minute time limit. If you want to get to Cosmic Fall from this level by clearing the Neutral mission, you have to let the clock run past five minutes; otherwise, the game will count getting to the goal as passing the Hero mission and sending you to Final Haunt. Manually selecting the Hero or Neutral mission in the pause menu does nothing to change which mission the game says you've cleared. This is the only stage where something like this happens.
- Sonic Rush Adventure: As opposed to nearly every other hidden island, where shallow water will hint at its location, there are two that require scouring the entire sea map to find. They're at the very top of the map, far from any other island, and there's no sign that they're up there.
- Sonic the Hedgehog (2006) had many omissions in the game manual; the game was severely rushed, so several of the things in the manual weren't actually in the game. But sometimes there are things you can do that you would have no idea was even possible. Rouge's bomb-planting move is the most infamous, as it's not mentioned anywhere in the game (and it's necessary to clear one section of Shadow's Kingdom Valley, as you have to find one of the three keys by bombing a stained-glass window).
- In Sonic the Hedgehog CD, to reach the Robotizer in Zone 1 of Wacky Workbench, you must stand on a block that looks like a crusher and let it slam you against the ceiling. Rather than crush you, it drops you into a secret area (although it looks very similar to the real Smashing Hallway Traps of Doom found later in Metallic Madness). Considering there is no way in game to know beforehand that the "crusher" is actually a transporter, let alone one that would take you to the Robotizer, the only way you could have found this out without looking it up would be sheer dumb luck.
Guide Dang It / Sonic the Hedgehog