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* AccidentalInnuendo: In early prototypes of the game, the special stages told you to "Get Blue Balls". Thankfully, the testers who worked on the game caught this (as well as laughed at it) and it was changed to "Spheres" for the final release.
* AnnoyingVideoGameHelper: Like with ''Sonic 2'', Tails is this when he's tagging along with Sonic. If you get a friend (or [[DoublePlay yourself]][[note]]This is extremely easy in the PC version or via UsefulNotes/{{emulation}}[[/note]]) to control Tails with the second controller, he can be ''extremely'' helpful. But if the AI controls Tails, then he'll get in your way, collapse platforms that you want to use, attack enemies and bosses half a second before you do (so they'll have MercyInvincibility by the time ''you'' hit them), and all-around make a nuisance of himself. The Giant Eggman Robo at the end of Death Egg Zone Act 2 (who otherwise borders on AntiClimaxBoss) is exponentially more difficult for this very reason.
* AntiClimaxBoss:
** Knuckles, especially considering in the intro he's able to punch the Chaos Emeralds out of Super Sonic. When you actually fight him, he's one of the easiest bosses in the second half of the game.
** Big Arms. While it's definitely a challenging boss, it doesn't come anywhere near the sheer scale of the [[VideoGame/SonicTheHedgehog2 Death Egg Robot]] as a final boss in the original ''Sonic the Hedgehog 3''. Of course, this is somewhat forgivable since ''3'' is technically only the first half of the game, and ''Sonic & Knuckles'' gives the game a proper FinalBoss. It's even easier in Knuckles' version due to being able to glide at the proper height and the Eggrobo attacking Knuckles more often than Robotnik, leaving itself more open.
** To an extent of the same reason above, the Giant Eggman Robo also falls under this. Unlike the [[VideoGame/SonicTheHedgehog1 Egg Crusher]] or the Death Egg Robot, you're able to carry rings over from the previous act, so you can actually fight it with rings on board for extra health, and if you have enough with all the Chaos Emeralds, you can also defeat it very easily with Super Sonic. The only main challenge comes when chasing Robotnik after the robot has been defeated, as the knockback for a successful hit can be enough to spike you into the crumbling pit.
* [[AwesomeBosses/VideoGames Awesome Bosses]]:
** Mecha Sonic Mk. II in Sky Sanctuary Zone. First you fight him in two Egg Mobile bosses from the previous two games, then you fight him straight-on. Even though he's easier than the Mecha Sonic in the previous game's Death Egg Zone, he has a much greater variety in movement, and you actually get to bounce backwards from Spin Dashing into him, giving a lot of options with fighting him and generally making the fight that much more exciting.
** The Doomsday Zone, setting the standard for final Super Sonic confrontations throughout the series. It's challenging, has great controls despite an UnexpectedGameplayChange, [[SugarWiki/AwesomeMusic great music]], and is a great reward for having completed all the Special Stages.
** Sure, it's pretty awesome when you fight him as Sonic, but Mecha Sonic Mk. II really kicks it up a notch when he becomes the final boss in Knuckles' story. At first, he uses pretty much the same tactics as when you fought him as Sonic, but then he gets right back up and uses the Master Emerald to transform into Super Mecha Sonic Mk. II. That's right, you don't just fight a simple Sonic clone robot, but a character (and a villain to boot) using a Super form.
* SugarWiki/AwesomeMusic:
** It's a Genesis ''Sonic'' game. [[AwesomeMusic/SonicTheHedgehog So pretty much the entire soundtrack qualifies.]] What's really cool is that, rather than using the same music twice per Zone, each Act 2 features a remixed version of the Act 1 theme.
** The [=IceCap=] Zone theme seems to be particularly popular, remixed so many times on Music/OverClockedRemix that it became a meme, resulting in an [[AprilFoolsDay April Fools']] album consisting of nothing but new [=IceCap=] mixes.
** The soundtrack also got additional respect once word got out that Music/MichaelJackson and his sound crew partially composed it. ''Many'' parts of each song are either heavily sampled from or inspired by his ''Dangerous'' album and standalone tracks.
** Though not technically part of the soundtrack, the Right Said Fred song "[[https://www.youtube.com/watch?v=lFQNFTeRjWc Wonderman]]" contains several references to the game and the music video is essentially a musical ad for the game. In the UK, it was a good chunk of the game's advertising.
** Some of the MIDI conversions in the PC version don't sound bad either, including [[https://www.youtube.com/watch?v=LKoU9i-XePg Marble Garden Act 1]] and [[https://www.youtube.com/watch?v=Ig2ILXi8KjA Lava Reef Act 2/Hidden Palace]].
** On November 16, 2019, an early prototype of ''Sonic 3'' was dumped and people were [[OlderThanTheyThink shocked]] that it contained ''Sonic & Knuckles Collection'' music; while some sounded incomplete, others like [[https://www.youtube.com/watch?v=BsMbaNoWTVc Carnival Night sounded amazing]]. Some people even consider [[FanPreferredCutContent these superior to the final Genesis tracks]], and to a greater extent, the versions utilized in the ''Sonic Origins'' release.
* [[Awesome/VideoGameLevels Awesome: Video Game Levels]]:
** On the ''Sonic 3'' half:
*** Hydrocity Zone. It's an underwater level, so if you've played the previous games, you're expecting a hard, long slog, right? You'd be wrong. It's a very fast wild water ride with Sonic blazing across the surface of the water, bouncing everywhere with the Water Shield, rolling down hills at ludicrous speed, getting caught in currents that fling you miles into the air, and has ''amazing'' music. It was the sole ''Sonic 3'' level that returned in ''VideoGame/SonicMania'' (barring Angel Island Zone, which received a smaller scale level in the ''Plus'' update).
*** [=IceCap=] Zone is a favorite among fans. It's quite fast-paced even for this game and has one of the biggest fan favorite music tracks of the series. It later got an excellent modern re-imagining in ''VideoGame/SonicAdventure''. [[ContinuityNod Sonic even gets to ride a snowboard again]] ([[IndyEscape this time up against an avalanche]]), and Tails can get in on the action as well. It was probably the most requested level from ''Sonic 3'' for both ''[[VideoGame/SonicGenerations Generations]]'' and ''[[VideoGame/SonicMania Mania]]'', and was, to the disappointment of many, ''not'' included in either game.[[note]]The exclusion of [=IceCap=] is most likely due to [[ScrewedByTheLawyers legal issues]] regarding the music with composer Brad Buxer, who recycled it from an unreleased track from his band The Jetzons.[[/note]]
** On the ''Sonic & Knuckles'' half:
*** Flying Battery Zone. This takes place in a massive flying airship, with awesome machinery or sky backgrounds whether you're inside or outside, and the sections alternate from fast-paced action to slower gimmick-based platforming. Finally, both Acts have some of the most ''awesome'' music in the series. Like Hydrocity, it's popular enough that it was chosen to be remade in ''Sonic Mania''.
*** Lava Reef Zone. Seeing the Death Egg stuck in the ceiling of the massive cavern and watching as the entire lava-filled cave suddenly turns to crystal is breathtaking, and the songs for both acts go along with it perfectly. It's popular enough that it was chosen to be remade in ''Sonic Mania''.
*** Sky Sanctuary is ''breathtaking''. The fact that it's nearly impossible to die on the stage makes it very easy to speedily run through the straightaways, with excellent platforming to boot. Also, it contains the excellent boss fights against Mecha Sonic. It was the level chosen to represent the combined game in ''Generations'', albeit lacking Mecha Sonic.
*** Death Egg Zone. Remember in ''[[Videogame/SonicTheHedgehog2 Sonic 2]]'', how Death Egg Zone in that game is a BossOnlyLevel with [[DroughtLevelOfDoom no rings]] and two stupidly hard bosses? Here, Death Egg has been fleshed out into a full zone where you first infiltrate the inside of the station, before making your way to the outside where the gravity goes in one of two ways and you take on ''four'' bosses in a row and as the entire Death Egg begins to collapse.
* BigLippedAlligatorMoment: Midway through Lava Reef Zone Act 1, you'll encounter some kind of big drilling robot which flashes and makes the "boss getting hit" sound when you hit it. However, it doesn't fight back and you will only be able to hit it once or twice before it drills a hole in the ground, falls into the lava, and blows up. You'll never encounter another one and the whole thing is never brought up again. [[spoiler:The robot reappears in ''Mania'' as the Act 1 boss of Lava Reef Zone, making this double as a ''very'' long example of ChekhovsGunman.]]
* BreatherBoss:
** The Guardian mini-boss of Sandopolis Zone Act 1 is pathetically easy. Even the fact that it's a PuzzleBoss doesn't help it much, as the solution to beat it is rather obvious. The main casualty may come from getting a Time Over if you take too long in the level beforehand.
** The Egg Inferno in Lava Reef Zone Act 2 after you get past the rather easy auto-scrolling platforming portion. The boss simply relies on jumping on moving platforms while avoiding mines that are easy to dodge. To make things even easier, there's also a Flame Shield in the lava falls before the boss that's easy to collect, negating the danger of landing in the lava altogether. The only thing is that it's a MarathonBoss due to being invincible to everything except [[HoistByHisOwnPetard its own mines]], so taking too long in the previous zone might end up locking you into losing a life from a Time Over. Knuckles altogether just skips this boss.
** As Sonic and Tails, Mecha Sonic Mk. II is surprisingly straight forward in all three battles, as the first two are directly lifted from ''Sonic 1'' and ''2'', and the third is a much easier version of the Silver Sonic fight since he can't hurt you without direct contact.
* BreatherLevel:
** If you're playing as Knuckles, Carnival Night Zone is a joke. The first act is quite a bit shorter than if you're playing as Sonic and/or Tails, and the second act isn't even ''half'' as long as it is then. No Barrel of Doom or even a ''boss'' for you to fight at the end of Act 2;[[note]]Unless you know how to access it by going out of the way to travel to Sonic & Tails's path.[[/note]] you can literally blitz through it in around 2-3 minutes, a sharp contrast to Sonic & Tails where it is one of the longest levels.
** [=IceCap=] is notable because it's quite short, but has difficult bosses.
** Mushroom Hill is this if you lock on both games, as it's the first level of ''Sonic & Knuckles''. It's quite easy and is shorter than most of the levels in both games. It helps that, as the first level of ''Sonic & Knuckles'', it had to functionally serve as a GreenHillZone.
** Hidden Palace Zone is pretty easy already as Sonic & Tails, but this is especially true when playing as Knuckles since it's a very short level and doesn't even contain any hazards, simply acting as a transition between Lava Reef and Sky Sanctuary.
** Sky Sanctuary, at least as Sonic or Tails, is nowhere near as grueling as Lava Reef or ''especially'' the Death Egg. Even the three bosses aren't too difficult, especially if you're familiar with the previous two games in the series.
* BrokenBase:
** Similar to [[VideoGame/SonicTheHedgehogCD two]] [[VideoGame/Sonic3DFlickiesIsland other]] ''Sonic'' games, there is a rift between fans of the Genesis soundtrack and fans of the PC/prototype soundtrack.[[note]]When ''Sonic 3 & Knuckles'' was first released on PC via the ''Sonic & Knuckles Collection'', the tracks for [[https://www.youtube.com/watch?v=zNCyFG988eU Carnival]] [[https://www.youtube.com/watch?v=heLtFnLqmUo Night]], [[https://www.youtube.com/watch?v=-_l_NOy_3dA Ice]] [[https://www.youtube.com/watch?v=dGZNfR2jImI Cap]] and [[https://www.youtube.com/watch?v=YhZL4woBvbE Launch]] [[https://www.youtube.com/watch?v=e0fX4YROAq8 Base]], as well as several other tracks such as [[https://www.youtube.com/watch?v=TKlkB87H8Ns Knuckles' theme]], [[https://www.youtube.com/watch?v=lhe2FWmbfyY the ending credits]] (only in ''Sonic 3'' standalone, as the ''S&K'' equivalents are still used in ''Sonic & Knuckles'' standalone and ''Sonic 3 & Knuckles'') and the [[https://www.youtube.com/watch?v=Ce-SKdVkeaM competition theme]] were replaced with renditions of the original tracks during development. This was only in the ''Sonic & Knuckles Collection'', however, as subsequent re-releases afterwards retain the Genesis tracks.[[/note]] Some utterly despise the PC/prototype tracks, either due to nostalgia towards the final Genesis tracks or finding them to be generic, lackluster and forgettable compared to the Genesis tracks. Others, however, tend to prefer the prototype/PC soundtrack instead, finding them to be catchier, more "Sonic-y" and better fitting and more in-line with the rest of the game's soundtrack than the final Genesis tracks do, which they feel stick out too much due to being the only tracks composed by Jackson's sound team (the rest being done by Sega's in house sound teams) and thus, were done in a noticably different style compared to the rest of the soundtrack (bigger use of samples, the act 2 arrangements not being as unique, etc).
** There is a debate amongst fans between the standalone ''Sonic 3'' exclusive tracks and the standalone ''Sonic & Knuckles''/''Sonic 3 & Knuckles'' tracks on which of the two sets is better and which one fits better with the game.
** Sonic's [[ArtEvolution redone sprites for the game]]. Some fans liked the more detailed sprites for Sonic, while others preferred the simpler looking sprites from the previous three games and the prototype and wished they kept them for the final version, if only for consistency. The fact that later "classic-style" games like ''VideoGame/SonicMania'' and ''[[VideoGame/SonicSuperstars Superstars]]'' have largely upheld the style from ''Sonic 1'', ''2'', and ''CD'' furthers the divide.
** It's not uncommon to see the fans debate whether the Blue Spheres are better or worse than the Half Pipe from ''Sonic 2'', and these debates can get quite heated because neither side wants to concede to the points the other makes.
** The Hyper forms. Either they're really cool upgrades of the Super modes and a great reward for collecting all the Emeralds? Or they're an unnecessary and overpowered GameBreaker that takes away the importance of the Super forms. Alternatively, should the Hyper forms come back in the games? Some fans would love to see them come back, while others feel it’s unnecessary (especially given how more powerful the Super forms have gotten) and would only run risk at causing power creep problems (which according to Creator/SonicTeam, is exactly the reason why they didn't keep the forms afterwards).
** Does the second zone of the game get pronounced as two words (Hydro City) or one word (as a pun for "velocity")? Fan debates can get very heated.
* CatharsisFactor: While he's ridiculously easy to beat, it's still satisfying to finally get revenge against Knuckles for all of the cheap tricks he's pulled since the start of the game.
* ContestedSequel: While most fans like both games, asking whether ''Sonic 3 & Knuckles'' is an EvenBetterSequel than ''VideoGame/SonicTheHedgehog2'' will get you a variety of answers, with both sides arguing over which game is the better 2D ''Sonic'' game. Some prefer ''Sonic 3 & Knuckles'' for its sheer scope, having 3 unique playable characters and the zones having a great mix of speed and exploration, while others prefer ''Sonic 2'' for its shorter length, more unique zone themes and the zones in general being faster to complete.
* ContinuityLockout:
** The game is rather light on plot, so this isn't too much of a concern, but a good chunk of the game's plot and elements such as the presence of Super Sonic and the Death Egg will likely be lost on you if you hadn't played ''VideoGame/SonicTheHedgehog2'' prior.
** You will most surely be lost on the events of ''Sonic & Knuckles'' if you hadn’t played ''Sonic the Hedgehog 3'' beforehand, given that the former is a direct continuation that picks up right where the latter left off. Fortunately, this isn't a problem with ''Sonic 3 & Knuckles'', since it combines both games into one.
* DemonicSpiders:
** Super Choppers, the piranha-like enemies from Hydrocity Zone. If you make contact with one, instead of damaging you, it'll latch on to you and start eating your rings. If you run out of rings (including when another enemy hits you), you die. Oh, and you can't jump while it's attached to you, either. Worse yet, you can actually have ''multiple'' Super Choppers attached to you at once if you're unlucky, which ''drastically'' increases the rate at which your rings drain away. The only way to escape is to shake them off by moving back and forth or force yourself into a ball by entering a chute or reaching the end of a conveyor belt that you hold on to.
** Orbinauts, black orbs with four spiked balls orbiting their body, returning from the original ''[[VideoGame/SonicTheHedgehog1 Sonic the Hedgehog]]'' in the Launch Base Zone. Unlike Star Pointers, their [[UndergroundMonkey ice counterparts]] in the previous level, Orbinauts are smart enough to keep the spiked balls instead of throwing them out and leaving themselves defenseless. While it is possible to defeat Chainspikes and Orbinauts as Sonic without taking damage through the careful utilization of the Insta-Shield, Tails and Knuckles cannot defeat these guys without either conventional or mercy invincibility. Amy in ''[[CompilationRerelease Origins Plus]]'' can make short work out of them with a well-timed Hammer Attack.
** Skorps, the brown mechanical enemies in Sandopolis Zone that attack by trying to sting you with their spiked tail, tend to be this for less experienced players. Their attack is aimed, making it extremely tricky to dodge even with good reflexes. Even if you do somehow dodge it, you better hope you destroy the Skorp in doing so, otherwise you'll have to watch that the tail doesn't hit you when it comes back.
** Chainspikes, the blue enemies in Death Egg Zone with four spikes positioned in the four cardinal directions. They move and attack very quickly, and if you don't hit them from a diagonal angle (easier said than done), their spikes will get you. Once again, Amy can destroy them with a Hammer Attack.
* DifficultySpike: Despite being shorter and having greater mobility thanks to his climbing and gliding abilities, Knuckles' playthrough is much more difficult than Sonic's, as his jump height is poorer, his unique paths are either more boxed-in or have a higher hazard density, and his bosses are far more aggressive and harder to hit.
* EnsembleDarkhorse: Despite only appearing a couple of times in this game, Mecha Sonic Mk. II has become incredibly popular, not only for his cool design but also for being the only robotic copy of Sonic to turn super in the games, something that not even the more prominent Metal Sonic has achieved ([[ComicBook/SonicTheHedgehogIDW or rather not in game canon]]). His popularity only increased after his depiction in the fan-made ''WebAnimation/SuperMarioBrosZ'', which made him the BigBad.
* FanPreferredCutContent:
** Although "Mushroom Hill" as a name is not hated, a number of fans wish it went by Mushroom Valley (its original name), instead, with many finding it to be a more distinctive name. ''Sonic 3 Complete'' even has it as the default name, with an optional patch required to use its final name.
** Many fans became surprised in November 2019 when a leaked prototype revealed that the alternate tracks once thought to be replacements exclusive to ''Sonic & Knuckles Collection'' (a PC port of the game) are actually the original tracks, with the final Genesis tracks by Music/MichaelJackson's sound team being last-minute replacements. Not only do many fans find them to be vastly superior to the MIDI-based rearrangements in the PC port, but some have gone on to prefer them over the final Genesis tracks. The prototype arrangements are also widely preferred by fans over the arrangements of them in ''Sonic Origins''.
* {{Fanon}}:
** A common fan theory as to why Knuckles got tricked by Eggman in this game is because he misinterpreted the mural in Hidden Palace as Eggman defending the Master Emerald from Sonic instead of Sonic fighting Eggman to retrieve it. While this could explain why he got tricked by Eggman for this game, it does not explain the numerous future times he got tricked by him.
** Speaking of said mural, many fans believe that during [[VideoGame/SonicAdventure2 Gerald Robotnik's studies on Angel Island]] he came across the mural and used its depiction of Super Sonic as the basis for Shadow's design. Another possibility for the inspiration for Shadow's look that gets cited is the statues of Sonic in Hydrocity Zone.
* FanonDiscontinuity: Not towards the game itself, but the Super Emeralds and Hyper forms. While the canon status of the Super Emeralds and Hyper forms remains unknown (though Iizuka has stated they simply disappeared into another dimension, presumably the special stage dimension), many fans opt to ignore them since future games don't acknowledge them[[note]]this is due to Sonic Team not wanting multi-tier power-ups and to risk devaluing the Super forms. Because of this, most alternative power-ups beyond Super Sonic post-''3 & Knuckles'' are unique forms that only appear once and never again. It wouldn't be until ''VideoGame/SonicFrontiers''' third DLC three decades later that Sonic Team would revisit the idea of [[spoiler:an upgraded Super Sonic in the form of Super Sonic 2/Super Sonic Cyber, but even so, they are treated as enhancements of Super Sonic rather than an outright upgrade like Hyper was, and it was a one-time case, as Sonic loses the enhanced super form permanently after defeating THE END]][[/note]]. It doesn't help that Hyper Sonic is not present in the original ''Sonic & Knuckles'' game, nor does it help that while the Hyper Sonic ending is the GoldenEnding, the Super Sonic ending contains [[TheStinger a post-credits scene]] leading into Knuckles' campaign, leading fans to conclude that Super Sonic is the "canon" outcome.
* FranchiseOriginalSin: Examples for this game are listed on the [[FranchiseOriginalSin/SonicTheHedgehog series page]].
* GameBreaker:
** The Glowing Sphere Bonus Stage. In ''Sonic 2'', Super Sonic was more balanced since every level had a finite number of rings and hence a hard time cap on how long you could stay super. In ''Sonic 3 & Knuckles'', however, the Glowing Spheres Bonus Stage allows you to earn oodles of rings with relative ease when you know how to play it; specifically, the Ring bubbles can give anywhere from 10 to 80 rings, allowing for a risk-free way of grinding for rings. You can also manipulate the system because the Bonus Stage you go to at a Starpost is determined not randomly, but by how many rings you're carrying. By playing only the Glowing Spheres Bonus Stage at each Starpost, it's possible to finish every Act with 999 rings, which are worth 999 seconds of Super transformation time. That's over 16 minutes, and the game's timer allows you only ''10 minutes'' per act.
** The Insta-Shield (which attacks enemies with increased range while protecting Sonic, and can be used anytime without a proper shield) and the Lightning Shield (which gives Sonic a DoubleJump) make most bosses a cakewalk. For instance, when facing the Launch Base Zone Act 2 boss (which is one of the final bosses in the standalone ''Sonic 3''), instead of facing Robotnik properly, you can double jump up to his "nest" area prior to the boss battle, and [[ZeroEffortBoss defeat him literally before the battle even begins.]]
** Having a second player play as Tails in Sonic & Tails mode can easily dispatch most enemies and bosses, since Tails can't lose rings when hit.
** In the boss battle for Angel Island Zone Act 2, you are completely immune to the boss's attack if you're equipped with a Flame Shield. This is also true for Angel Island Zone Act 1's boss, but only if you're Sonic and/or Tails (this boss only uses its front flamethrower for those two; it adds its missiles for Knuckles).
* GoddamnedBats:
** Blastoid can be a bit of a {{goddamned bat|s}} in Hydrocity Zone. Especially since he will inevitably hit you at least [[RuleOfThree three times]] throughout the level. Most likely even more, considering his placement.
** Batbot can be a literal goddamned bat in Carnival Night Zone, as it follows you forever and therefore can end up in some inconvenient places if you don't get rid of it, knocking you back.
** Skorp, the scorpion in Sandopolis Zone, teeters between this and DemonicSpiders depending on experience. Touching the spiked ball on its tail get the player character hurt, and it will also use the tail and try to attack Sonic at an aimed angle. And it's ''very'' accurate.
** The ghostly Hyudoros in Sandopolis Zone Act 2, especially when it is dark -- they grow big and attack in numbers, and they can't be killed off permanently. And since it is Sandopolis, you'll often have to deal with them alongside the aforementioned Skorps. Have fun.
* GoddamnedBoss: Death Ball, the first of the two bosses faced in Death Egg Zone Act 2, is not a hard boss by any stretch of the imagination, but is ''incredibly'' annoying and a massive time sink. Unlike every other boss in the game, it's incapable of directly hurting Sonic, but Sonic also can't hurt it due to the bumper on it that always locks on to Sonic's position. The only way Sonic can be hurt is through the mine tanks that the Death Ball drops, which are also the method of hurting the boss. Problem is, there's only two ways that they can hurt the Death Ball, both involving the [[GravityScrew gravity inversion pods]]. One is to flip gravity and have their spiked tops hit the Death Ball, which isn't a reliable method due to the fact that both the Death Ball and the mine tanks are constantly moving, neither being in sync with each other. The second is to flip gravity and get them stuck in the ground, then Spin Dash into them to launch them into the air and have them land on top of the Death Ball, which also isn't reliable due to the fact that Spin Dashing into them causes the mine tanks to be launched in an arc motion. Both methods also run Sonic the risk of getting hurt, as direct collision with the Death Ball causes the mine tanks to launch three spikes at Sonic in different directions.
* GoodBadBugs:
** The points from destroying successive robots or bricks went 100, 200, 500, 1000, and stays at 1000. But there is a mechanic left over from ''Sonic 1'': upon destroying the 13th object, the score jumps to 10,000. There is only one area in the original game this can be done (you can destroy 16 blocks in a row if you do it right), but there's also one in ''Sonic 3'': in Launch Base Zone, right near the beginning, there's an alarm that summons a flying robot. Doing a Spin Dash in that alarm and staying there to keep setting off the alarm will summon robot after robot, which fly right into Sonic and are destroyed. It's possible to rack up over 10 million points (200 lives) until either the life counter or score maxes out.
** In ''Sonic 3'' by itself, through some stage select hijinks, you can get the game to play music from the wrong stage.
** Have you ever wanted to hear the ''Sonic & Knuckles'' mid-boss theme while fighting a mid-boss in standalone ''Sonic 3''? [[https://info.sonicretro.org/Sonic_the_Hedgehog_3/Bugs#Incorrect_boss_music_plays_after_avoiding_drowning Here's how]]. Also, this fight plays the wrong (major boss rather than mid-boss) music to begin with...
** In Launch Base Zone, there is a part of the level where Robotnik in his Eggmobile tries to fly off with a box. However, he only flies off if the player jumps up to a certain height. As such, if the player is playing as Sonic and Tails, he can use the 2P controller to control Tails and attack Robotnik. After 256 hits, Robotnik pops like a regular badnik and releases either a blue bird or a white chicken. See the video [[https://www.youtube.com/watch?v=fo8G_-ti170 here]]. Now we know the real reason as to why he was called ''[[{{Pun}} Egg]]''[[{{Pun}} man]].
** When ducking, you'll scroll the screen downwards. With some precise movements, it's possible to go inside the floor, possibly skipping some sections of the level.
** In ''Sonic 3'' alone, you can bounce with the Water Shield as Super Sonic. This got fixed in ''Sonic 3 & Knuckles'', however, and doesn't work with the other shields in ''Sonic 3'' alone.
** In Hydrocity Zone Act 1 for ''Sonic 3'', if Tails died by drowning approximately one second before the message "Act 1 Completed" appeared, there's a chance he won't respawn for the rest of the next act, so good luck in defeating Robotnik by yourself. You can make him reappear by entering and then finishing a Special Stage or any Bonus Stage, however.[[note]]Whether you win or not, in the case of entering Special Stage.[[/note]]
* GrowingTheBeard: While ''VideoGame/SonicTheHedgehog2'' did a lot to improve the formula for the series, this is widely considered when 2D Sonic really hit its stride and subsequent entries tend to get compared to this game.
* HarsherInHindsight: When starting Sandopolis Zone Act 2 with Knuckles, it is completely dark and the capsule containing the ghosts is already open, meaning the ghost are ready to attack. Then we learn in ''VideoGame/SonicAdventure2'' that Knuckles is supposedly afraid of ghosts.
* HilariousInHindsight:
** The excessive amount of [[GigglingVillain diabolical giggling]] that Knuckles does throughout this game whenever he thwarts Sonic's quest becomes even funnier after the release of ''VideoGame/SonicAdventure'' when his theme song insistently declares "Unlike Sonic I don't chuckle!" Yeah Knuckles, ''sure'' you don't. Ironically, in a prototype uncovered in November 2019, Knuckles actually ''doesn't'' chuckle in his introduction, and instead dares Sonic to pursue him with a serious look on his face.
** Mecha Sonic Mk. II, being taller and with bigger spikes than Sonic at the time, resembles an actual mechanical doppelgänger of Modern Sonic rather than Classic Sonic.
** One fan, as part of a series of classic zone remixes inspired by ''VideoGame/SonicTheHedgehogCD'''s past/present/future renditions, did a [[https://youtube.com/watch?v=9-y0nJmcWQs past version of Launch Base]] which was a remix of the track from the ''Sonic & Knuckles Collection'' port. A year later, it was revealed in a prototype for ''Sonic 3'' that this was actually an unused track for the zone before being replaced, which makes the aforementioned fan remix very appropriate as the track is literally from the game's past.
** Every fanmade Mega Drive/Genesis rearrangement of the tracks from the ''Sonic & Knuckles Collection'' done prior to the revelation have become this in light of a prototype revealing that they were originally intended to be in the original Mega Drive/Genesis game prior to getting scrapped.
** A prototype for the game contains a couple of experimental moves for Sonic such as ring-tossing and a primitive version of what players eventually came to know as the [[VideoGame/SonicMania Drop Dash]].
** [[https://www.gameinformer.com/b/features/archive/2016/10/10/how-sonic-the-hedgehog-3-became-two-games-sonic-and-knuckles-lock-on-technology.aspx The developers decided against implementing proper Knuckles playability]] when locked onto ''Sonic the Hedgehog 1'' because they believed fans wouldn't enjoy trekking the [[EarlyInstallmentWeirdness more linear level structure]] with his mechanics. In later years, {{Game Mod}}s inserting Knuckles (and multiple other characters) into ''Sonic 1'' became a reality due to fans. Amusingly, Stealth, the person responsible for the first proper ''Knuckles in Sonic 1'' hack, also worked on the 2013 mobile port of ''Sonic 1'', which officially adds him and Tails as playable characters.
** Crustle from ''Franchise/{{Pokemon}}'' resembles the exploding Iwamodoki badnik in Lava Reef Zone. While a hermit crab monster isn't uncommon, what clinches the connection is that both use prism-shaped rocks as shells.
** By locking on a ''Sonic 2'' cartridge with ''Sonic & Knuckles'', ''Sonic 2'' turns into ''Knuckles the Echidna in Sonic the Hedgehog 2''. In the film canon, Knuckles makes his debut in [[Film/SonicTheHedgehog22022 the second film]].
* HypeBacklash: Due to the massive amount of praise that the combined game gets, it isn't uncommon for some to call the game overrated.
* IKnewIt: Many fans predicted that the prototype/PC tracks would be used in the ''Origins'' remaster of ''Sonic 3 & Knuckles'' instead of the final Music/MichaelJackson/Brad Buxer tracks due to legal issues surrounding the latter. Katie Chrzanowski, Sega of America's social media coordinator, confirmed that this would be the case during one of the official ''Sonic'' livestreams. A number of fans also predicted that they wouldn't be using the arrangements from the leaked November 1993 prototype, which also ended up being true.
* ImprovedByTheRecut: While ''Sonic 3'' and ''Sonic & Knuckles'' are considered to be good standalone games, many fans consider the combined recut of the game, ''Sonic 3 & Knuckles'' (which you get by locking ''Sonic 3'' onto ''Sonic & Knuckles'') to be the superior version of the game, due to it combining both games into one seamless experience (which was what Creator/SonicTeam intended until they were forced to split it into two games due to time and hardware constraints), on top of fixing numerous bugs in ''Sonic 3'' and having features not found in either game, such as upgraded Super forms and the ability to save in the ''Sonic & Knuckles'' zones. It is likely because of this that more recent rereleases of the game, such as the Steam release in 2011 and the port in ''Sonic Origins'', opt to have ''Sonic 3 & Knuckles'' instead of the standalone titles.
* JustHereForGodzilla:
** A significant number of fans just play the game for the extra forms for the playable characters. In fact, the Hyper forms are so popular that many fans are still waiting for them to return in a future game.
** Among music fans, the revelation that Music/MichaelJackson and his sound team contributed to the ''Sonic 3'' soundtrack brought a great amount of renewed attention to the game, especially after Jackson's death in 2009, with many checking the game out solely for the sake of hearing the songs that Jackson may or may not have worked on.
* MemeticBadass: Mecha Sonic, the boss of Sky Sanctuary Zone. This is mostly due to its involvement as the main antagonist of the webseries ''WebAnimation/SuperMarioBrosZ'' where it's a complete AdaptationalBadass, but also it being the first villain to ever achieve a super form.
* MemeticMutation:
** Music/MichaelJackson mashups.[[labelnote:Explanation]]Long-rumored among fans and eventually confirmed by Yuji Naka, Jackson's involvement with the soundtrack of ''Sonic 3'' has inspired many a ''Sonic''/MJ music mashup, with some ''[[SugarWiki/AwesomeMusic interesting]]'' results.[[/labelnote]]
** & Knuckles.[[labelnote:Explanation]]Playing off the fact that locking ''Sonic 3'' onto ''Sonic & Knuckles'' retitles the game ''Sonic 3 & Knuckles'', fans took to appending the "& Knuckles" suffix to other works' covers. Often crossed over with "[[VideoGame/ShinMegamiTenseiIIINocturne Featuring Dante from the Devil May Cry series]]''.[[/labelnote]]
** [[GameBreakingBug Eggman's]] [[UnintentionallyUnwinnable diabolical]] [[HandWave traps.]][[labelnote:Explanation]]A shorthand developer's excuse in the manual for ''Sonic the Hedgehog 3'''s rushed development and buggy state.[[/labelnote]]
** [[ScrappyMechanic The Barrel of Doom]].[[labelnote:Explanation]]When going through Carnival Night Zone Act 2, players will encounter a barrel that can be moved up and down while standing on it by pressing in the respective directions, so you move it enough to jump through an open space. [[GuideDangIt Nothing else in the game works like this nor is this described in the manual somewhere]], leading to one of the most infamous obstacles in ''Sonic'' history.[[/labelnote]]
** "Knuckles chuckles."[[labelnote:Explanation]]One of the tracks in ''VideoGame/SonicAdventure'', "Unknown from M.E.", is a BoastfulRap from Knuckles that includes the line "Unlike Sonic I don't chuckle." Fans were quick to point out ''Sonic 3'', where within the first minute of gameplay and in numerous other parts Knuckles does, in fact, chuckle.[[/labelnote]]
** Doilus Stage.[[labelnote:Explanation]]A minor meme surrounding a glitch that occurs when you attempt to exit the Gumball Machine bonus stage in the standalone version of ''Sonic the Hedgehog 3''. The "Bonus Stage" title card corrupts into "Doilus Stage", and the stage infinitely repeats itself until you reset the game. Fixed in ''Sonic 3 & Knuckles''.[[/labelnote]]
* SugarWiki/MostWonderfulSound:
** Collecting a Chaos/Super Emerald. Collecting them all presents the player with an even more triumphant jingle.
** Going into [[SuperMode Super or Hyper Mode]]. Sonic gives off a high-pitched whine when he enters The Doomsday Zone, the only such instance in the entire game.
* OlderThanTheyThink:
** For the vast majority of the game's life, virtually everyone believed that the unique tracks heard in the ''PC Collection'' were last-minute replacements thrown together when Sega had to cut the Michael Jackson/Brad Buxer tracks from the game. However, a prototype build released in November 2019 revealed that the ''opposite'' was actually true: the ''PC Collection'' tracks actually came ''first'', with the MJ/BB tracks being added later on.
** The Special Stage theme, as well as the entire idea of colored spheres, didn't actually originate in this game; rather, their (intended) debut was in the unreleased arcade game ''VideoGame/SegaSonicBros'' [[https://youtu.be/bFEwSZdORmA?t=1515 Behold!]]
* PolishedPort: Music issues aside (detailed in TheyChangedItNowItSucks below), the port in ''Sonic Origins'' is regarded by fans to be the highlight of the compilation and the definitive official way to play the game. It brings in the numerous refinements from the previous remastered ports such as widescreen support and smoother animations, adds in the drop dash from ''VideoGame/SonicMania'', fixes several bugs (and more via patches), restores the Big Arms boss for Sonic and Tails, has new sprites for Super Sonic, and adds in various quality of life improvements that greatly improve the game (such as having Super Sonic be activated by a separate button like ''Mania'' and adding new animations for Sonic and Tails on the Barrels in Carnival Night to make it clearer what you're supposed to do on it).
* RealismInducedHorror: The first zone (Angel Island Zone) starts out as just a tropical island, but Eggman launches a massive napalm attack which in turn creates a huge wildfire. This seems a lot darker in general than his usual goofy plots such as turning people into robots or building giant space stations with his face on them. It's also [[DoesThisRemindYouOfAnything pretty obviously meant to be reminiscent of the Vietnam War]], and considering you never see the zone after, you also [[OffscreenInertia wonder if the whole place just burned down eventually.]]
* SacredCow: Before Sonic Mania was released, aside from a small faction that preferred the level design of ''Sonic 2'', ''Sonic 3 & Knuckles'' was generally held as [[EvenBetterSequel the pinnacle of perfection by the fanbase]], and even lightly criticizing it was bound to get you backlash.
* ScrappyMechanic:
** The level select code in ''Sonic 3'' standalone is infamous for being unforgiving to input. You have to press ↑ ↑ ↓ ↓ ↑ ↑ ↑ ↑ when the title theme starts, but before Sonic lands and uncurls from his ball form, meaning that you have enter the code in about ''two seconds''. Worse, the two-second window has [[http://info.sonicretro.org/Sonic_the_Hedgehog_3/Hidden_content#SEGA_screen_technical_details an absolutely preposterous number of lag frames]] during which your input is disabled, meaning that even if you do push all the buttons fast enough, the game might not have registered them. In comparison, the ''S&K'' and ''S3&K'' versions of the code simply require you to input directional commands while hanging onto an object, with no requirement to enter the code so quickly.
*** This is resolved in the ''Sonic Origins'' remaster of the game, where the requirement for the code to be entered comes up when the "Press Button" prompt appears.
** Despite the levels being between two and three times the size of what was seen in the previous ''Sonic'' games, the ten minute time limit remains. Some levels are legitimately difficult to finish without losing a life to the time limit, particularly the second acts of the Carnival Night and Sandopolis Zones. Carnival Night Zone Act 2 also contains the infamous "Barrel of Doom", responsible for keeping many players from continuing if they [[GuideDangIt didn't have a guide on hand]] or luck in finding out how to operate it.[[note]]In order to operate it, you have to press Up and Down while standing on top of it, in sync with the barrel's vertical direction.[[/note]]
** Grabbing an invincibility power-up disables Sonic's Insta-Shield and shield jumps for the duration of the effect, forcing you to wait out the invincibility if you're trying to get somewhere that requires an elemental shield or Tails to jump to. It's understandable that having a shield disables the Insta-Shield (since the same command for an Insta-Shield is now used for shield jumps), but there isn't much of a practical reason why invincibility means you can only perform basic jumps. Going Super or Hyper as Sonic also disables the shield jumps, though he at least has a higher jump in either form and a has unique double-jump when Hyper.
** While the Super/Hyper modes are game breakers par excellence, the fact that pressing the jump button twice is what triggers them is more of a problem because this is the same command that is used for actions like Sonic's Insta-Shield or Tails' flight.[[note]]This and all other related issues are fixed with {{Game Mod}}s or {{Fan Remake}}s like ''Sonic 3 Complete'' and ''Sonic 3 Angel Island Revisited'', which not only change it so you press a different button after jumping to transform, you can also turn off the transformation by again pressing that button. The ''Origins'' version also triggers the transformations the same way as ''Complete'' and ''A.I.R.'' but can't turn it off by doing the same thing.[[/note]] So if you have enough rings to go Super, you can't use character-specific mechanics without doing so. It's particularly bad for Knuckles players, as his flight and climbing are often mandatory to traverse the levels. And since emerald collection is permanent, the only way to avoid this is to either trigger the Super Emeralds intro cutscene (which takes away Super mode) or, if you already have a full set of Super Emeralds, start an entirely new file. This is also the case for the 2013 (but not ''Origins'') remake of ''Sonic 2'', though Sonic doesn't have this problem there due to not having the Insta-Shield.
* SelfImposedChallenge:
** ''Sonic 3'' may be the first game in the series to allow saving, there is still a No Save slot in case you prefer to explore the areas all over again like the previous titles. It's an [[BladderOfSteel even bigger challenge]] in ''Sonic 3 & Knuckles''.
** While ''Sonic 3 & Knuckles'' allows you to get Super Emeralds and to get the Hyper Sonic form, you can still ignore the Giant Rings starting from Mushroom Hill Zone (you still have to get the Chaos Emeralds on the previous zones, however) to keep the Super Sonic form until the end of the game. This makes the Doomsday Zone ''way harder'', as you can't dash in the air.
** Exclusive to the ''Origins'' version is a sound test code by entering 00 eight times in a row, causing a ring dropped sound to play. This will remove every ring, [[NoItemUseForYou item box]], and Special Rings, turning you into a OneHitPointWonder for the entire duration of the game. This effectively also disables entering bonus and special stages, so continues are also normally disabled should you try this challenge on Classic Mode. Due to being a level select exclusive code, you cannot [[OnlyOneSaveFile save your progress]], either. Just don't enter The Doomsday Zone with this code active, as that level becomes UnwinnableByDesign without rings.
* SequelDifficultyDrop: ''Sonic 3'' is significantly shorter and easier than ''Sonic 2'', consisting of only six 2-act zones that never approach the sheer hell that the latter game's late levels approached, with the final boss [[AnticlimaxBoss both looking and feeling more like a typical boss than a serious endgame challenge]]. The fact that it's actually only the first half of a much larger game explains why.
* SequelDifficultySpike: ''Sonic & Knuckles'' is significantly harder than ''Sonic 3'', due to essentially being the second half of the same game- the levels are longer and more complex, and the bosses have more difficult attack patterns. That said, Mushroom Hill Zone is easier than Launch Base Zone, although the difficulty ramps up before long.
* ShockingMoments: Angel Island being engulfed in flames, Sonic being nearly bombed by an airship, Eggman destroying an entire temple, Sonic snowboarding down a tall mountain, Eggman stealing the Master Emerald, and Super Sonic chasing Eggman down through space. And may we say that all this was achieved on the Platform/SegaGenesis?
* SignatureScene:
** The intro featuring Super Sonic flying through Angel Island Zone and getting hit by Knuckles, who [[BagOfSpilling takes the emeralds]], laughs at him, and runs away.
** The infamous Barrel of Doom in Carnival Night Zone Act 2, for [[GuideDangIt prematurely ending several playthroughs]].
** Sonic snowboarding down the mountain at the beginning of [=IceCap=] Zone. So iconic in fact that it was recreated in ''VideoGame/SonicAdventure'' years later.
** The Lava Reef Act 2 for its gameplay and story-wise intensity (the Death Egg is about to be launched again and makes the dry lava melt), and for [[BewareTheSillyOnes its dark portrayal of Eggman]] in the background.
** Super/Hyper Sonic chasing after Eggman in space as he tries to escape with the Master Emerald.
* SpiritualSuccessor:
** Hydrocity Zone to Chemical Plant Zone from ''Sonic 2''. They're both very vertical high speed levels with lots of tubes, slopes, and water. This was even confirmed in the Japanese ''Sonic Jam Official Guide'', where it's outright stated that it was based on Chemical Plant Zone.
** Flying Battery Zone, simply put, is what Wing Fortress Zone from ''Sonic 2'' should've been. Carnival Night Zone would ''appear'' to be this to Casino Night Zone from the name, but besides being brash and colorful levels they don't share much in detail.
** Several zones reuse ideas from dropped levels from Sonic 2. Angel Island Zone and Mushroom Hill are this to the dropped level Wood Zone (as well as Jungle Zone from the [[VideoGame/SonicTheHedgehog18Bit 8-bit version of]] ''[[VideoGame/SonicTheHedgehog18Bit Sonic the Hedgehog]]''), Sandopolis and [=IceCap=] Zone are this to the dropped Dust Hill and Winter Hill Zones (although they aren't connected). Lava Reef and Hidden Palace are this to Hidden Palace Zone (in a strange variation, Lava Reef reuses graphical ideas from it, whereas Hidden Palace only uses the name. Elements of Hidden Palace were also used in Quartz Quadrant from Sonic CD).
* SuspiciouslySimilarSong:
** The Blue Spheres main menu/Competitive Results/"Continue?" screen to "Honk Around the Clock" from ''Series/SesameStreet''.
** The bass riff in the Genesis version of Launch Base Zone's theme to that of the instrumental version of [[Music/NaughtyBoys "Wild Ambitions"]] by Music/YellowMagicOrchestra.
** Ice Cap Zone's theme is nearly identical to "[[https://www.youtube.com/watch?v=q9sdsclDwas Hard Times]]" by The Jetzons.
** [[https://www.youtube.com/watch?v=_T7hdIh-gtw Flying Battery Zone's theme]] borrows considerably from [[https://www.youtube.com/watch?v=usE5qz_5wJs the airship theme]] in ''VideoGame/TheRevengeOfShinobi''.
* ThatOneBoss:
** The Tunnelbot can be problematic with Knuckles. Not only does his shorter jump make it harder to reach, but the spikes platform also retracts and protrudes every second, meaning you have a shorter window to properly hit the boss while using a character that takes longer to do so.
** The Egg Drillster Mk. II can be annoying to defeat with Tails alone. While Knuckles faces a entirely different boss and Sonic can hop on Robotnik's head with no problem, Tails must carefully fly towards the lower part of his pod taking care to not hit either the drill in its front or (if you couldn't hang onto a Fire shield) the flaming exhaust on its back, since his tails are the only part that can cause damage while flying. Oh, and since you cannot regain lost rings when hit, getting hit twice (or 3 times with a shield) is fatal. Considering that Tails is meant to be the game's de facto easy mode, having such a massive DifficultySpike exclusive to him alone is rather jarring, to say the least[[note]]You can at least shorten the fight by getting as many hits in on Robotnik as you can when he first appears and starts drilling into the ground, since the damage dealt here carries over into the boss fight proper.[[/note]]. If that wasn't enough, there's no rings in the BossRush in ''Sonic Origins''.
** The Egg Gravitron can be a real pain without the Lightning Shield. When Eggman lowers to pick up the orb, that is the only opportunity you have to hit him, and it's very easy to accidentally take a hit afterward because of the shape of the mech. Also, when he drops the orb, it bounces to the side a bit. Furthermore, you've got to be very careful where you let him drop it because it's possible for him to go offscreen if he's close to the edge of the screen. No rings for you on the BossRush in ''Sonic Origins'' as well. It is much easier when fought with Amy as her hammer attack can damage the Egg Gravitron with less risk of hitting the attachements itself.
** Both the Big Icedus and the Egg Froster of [=IceCap=] Zone are considered this by some players; the former because it's hard to hit, while the latter's freezing attacks are randomized. The latter is even worse as Knuckles as it can retract the platform after bringing it down, which can also crush and instantly kill you if you're frozen underneath it. There's also no rings for the Egg Froster on the BossRush in ''Sonic Origins''.
** The "final boss" of the ''Sonic 3'' half, a.k.a. Big Arms, can be one of the most intensely frustrating fights, especially for newer players. Eggman's hitbox is so miniscule yet it's covered on the top by spikes and on the bottom by the shoulder of the arms, and you have to dodge the hands or else he grabs you and you take damage. If ''that'' wasn't enough, he can even damage ''Super Sonic''.[[note]]This is removed in the locked-on game and in ''Origins'', suggesting that it was a programming error.[[/note]] With careful usage of the Insta-Shield, the fight can be a lot easier, but it's likely for all of the previously stated reasons why this boss was removed from Sonic and Tails' paths in the combined game.[[note]]It's still there in the Knuckles path, but it's much easier thanks to Knuckles' gliding. Furthermore, the ''Origins'' version restores the boss fight for Sonic and Tails.[[/note]]
** The Egg Scrambler as Knuckles. This part definitely teaches you not to spam the jump button as floating can make this fight a lot harder. Also, rebounding to get your rings back is nearly impossible due to the side scrolling nature of the fight, so getting hit means you have to perfect the rest of the fight. Per the usual, no rings on this boss (including Sonic/Tails' version) on the BossRush in ''Sonic Origins''.
** Red Eye, the miniboss of Death Egg Zone Act 1, has two phases. It can be rather tricky trying to fight it without getting hit, especially during the first phase with the orbs. Other minibosses in this game tend to be easy. This boss is much more trivial with Amy as she can hit the eye during the first phase even when the orbs are defending it.
* ThatOneLevel:
** While Hydrocity Zone Act 2 is fast, fun, and has incredible music, the first 20 seconds were [[AdvancingWallOfDoom pretty damn scary]] for many players.
** Carnival Night Zone Act 2. The level seems designed to waste your time, so that you'll invariably run out the timer while fighting Robotnik (unless you use Sonic's Insta-Shield against him). And it features the infamous Barrel of Doom. Thankfully, if you lock on both games, it becomes a lot more manageable.
** [=IceCap=] Zone Act 1 is another "waste a lot of time" level. The level features very little fast running, and it mostly revolves around tricky puzzle solving.
** Both acts of Sandopolis Zone are really long levels. The second, in particular, is a slow-paced puzzle stage in a similar vein to the first game's Marble Zone, only with much more elaborate puzzles, and needing to constantly turn on the lights to prevent invincible ghosts spawning. In the original version, or Origins' Classic Mode, running out the 10 minute timer is a legitimate threat.
** Death Egg Zone Act 2, the last full level for Sonic and/or Tails, has a lot of dangerous traps, an upside-down gravity gimmick, and many star posts that [[OneHitPointWonder don't have rings near them]].
* ThatOneSidequest:
** The Blue Sphere special stages in the ''Sonic & Knuckles'' half (which become the special stages needed to get the Super Emeralds in ''Sonic 3 & Knuckles'') are far less forgiving than those in the ''Sonic 3'' half and some of them can be incredibly frustrating, with the stages often having very weird and tricky level design and requiring both quick reflexes and perfect and precise timing in order to clear them, especially if you attempt to go after that perfect bonus. It doesn't help that the special rings in the ''Sonic & Knuckles'' zones are more sparse and harder to locate than those in the ''Sonic 3'' zones (especially after Mushroom Hill), nor does it help that if you fail, they have no chance of respawning until you complete the game, which makes their harder difficulty that much more of a headache. The port in ''Sonic Origins'' does make things a bit more bearable by giving you the chance to retry them at the cost of coins, but it doesn't make them any less frustrating.
** Of these, the blue Super Emerald course (second from the left) is among the most brutal. There's exactly ''one'' path to take that will result in success (any other route will eventually catapult you back into red spheres you'd previously collected, ending the stage), all blue spheres are in straight lines only (collectable rings are boxed inside bumpers, making it very tricky to jump out, nab them, and then safely jump back in to resume the course), and there is practically no empty space anywhere so you can't backtrack to pick up any missed spheres. Better yet, getting from one track to the next requires you to time your jumps perfectly to launch over to the next one; too late and you'll overshoot the yellow sphere, too soon and you'll miss the last blue one, which automatically means you've failed the course because, as mentioned, the layout makes do-overs impossible.
* TheyChangedItNowItSucks:
** The PC port known as ''Sonic & Knuckles Collection'' bothers some players because all the music is in MIDI format (though with an FM synthesizer it sounds much closer to the original Genesis tunes), and several music tracks are different from the released version, including [=IceCap=] Zone. That said, several of the alternate tracks can be quite good in their own right. Look them up and judge for yourself.
** It was eventually discovered via the Nov 3, 1993 prototype of ''Sonic 3'' that the aforementioned "replacement" tracks were actually the original ones all along, which now caused this sentiment towards the Jackson/Buxer tracks in certain parts of the fanbase, mostly for a purely practical reason: had the tracks not been replaced, ''Sonic 3'' wouldn't have spent over a decade in a legal limbo.
** The soundtrack getting changed to the Prototype/PC tracks in ''Sonic Origins'' was always gonna receive this reception regardless due to how fond fans are of the Michael Jackson/Brad Buxer tracks, but even fans who don't mind the prototype tracks getting used were unhappy that instead of simply reinserting and polishing up the arrangements from the November 3rd, 1993 prototype, Sega instead used different versions that are [[https://forums.sonicretro.org/index.php?threads/the-sonic-origins-music-situation.41806/ highly likely to be from an even earlier prototype]]. These versions immediately received criticism from the fandom, with many regarding them as being inferior to the arrangements from the leaked prototype, on top of being poor quality in their own right.
** Likewise, there is a brand-new theme for Super Sonic in the ''Origins'' version, meant to replace the usage of the repetitive Invincibility theme being used for the transformation instead of getting its own theme like in ''Sonic 2''. Unfortunately, it has been received just as bad as, if not ''worse'' than, the ''PC Collection'' arrangements. How? Instead of using the original Genesis instruments of ''Sonic 3 & Knuckles'' as a base, Jun Senoue instead reuses the almost universally-reviled synthetic Genesis sounds that were used in ''VideoGame/SonicTheHedgehog4'', causing it to sound very out of place with the rest of the soundtrack. Making matters more perplexing is that in the Prototype version of ''Sonic 3'', there was an unused song that had been used in fan-made ROM hacks as a new theme for Super Sonic which had been generally well-received. This song does make an appearance in ''Origins'', but it is used for the difficulty rating screen for ''New Blue Spheres''.
* ToughActToFollow: Sega would spend ''decades'' trying to replicate the success of ''Sonic 3 & Knuckles''. It didn't help that this was the last mainline 2D game before Sonic went 3D, with incredibly mixed results.
* UnfortunateCharacterDesign:
** The Egg Drillster Mk. II, which has a long drill in between two spherical jets.
** The Bowling Spin in Carnival Night Zone, as well as the Egg Hanger of Flying Battery, are both rather Freudian in design. The shape of the flames that come out of the Flying Battery boss don't help.
* ViewerGenderConfusion: When he debuted in the ''Sonic 3'' half, many players mistook Knuckles for a girl due to his pinkish fur and long hair. He's supposed to be red, with quills styled into dreadlocks, but that isn't readily apparent from his sprite. His appearance in ''Sonic & Knuckles'' makes this more clear, in particular giving him more vibrant red fur.
* ViewerPronunciationConfusion: Hydrocity Zone is notorious among fans for its ambiguous pronunciation, with many debating whether "Hydrocity" is meant to be read with a long "o" (i.e. "Hydro City," aligning with its aquatic setting) or a short one (rhyming with "velocity," tying in with the Sonic games' focus on speed). Several official Japanese sources point to the former, but many non-Japanese fans stick with the latter. This was acknowledged by [[https://twitter.com/SEGA/status/1535669223023951873 an official poll held by Sega]], where the results were roughly split down the middle even after nearly 100,000 votes.
* VindicatedByHistory: ''Sonic 3 & Knuckles'' fell into this as a result of the game [[OneGameForThePriceOfTwo being split into two due to time and budget constraints]]. While ''Sonic 3'' was positively received, it received some flak for not evolving the formula much. Perplexingly the game was also seemingly much shorter than ''Sonic 2'' and ended with the story arc concerning Knuckles and Angel Island on a {{Cliffhanger}}, until it was revealed to be merely "part one" of a full game. Furthermore, while ''Sonic & Knuckles'''s lock-on technology was acclaimed at the time of release, it was more for its replay value rather than for how it transformed ''Sonic 3'' and ''Sonic & Knuckles'' into one complete package. It was only in later years when reviewers revisited the two games, did they realize that when they were presented as one title, ''Sonic 3 & Knuckles'' [[EvenBetterSequel was an incredible refinement of the formula]] that took things [[SerialEscalation even further]] than ''Sonic 2'' did, with enhancements in nearly ''every'' aspect, which includes better gameplay and graphics, varied playable characters, larger and more balanced level design, and a more compelling story and presentation, among others. Nowadays, both games combined are widely referred to as the true and complete version of ''Sonic 3'', and while some reviewers and the general public [[FirstInstallmentWins are more inclined to point towards the first two titles]] as the series' best games, more reviewers have come in agreement with fans by appointing ''Sonic 3 & Knuckles'' as the pinnacle of the series.
* SugarWiki/VisualEffectsOfAwesome: The game demonstrates 2D animation techniques that were unheard of for the [[MediaNotes/The16bitEraOfConsoleVideoGames 16-bit era]]. Highlights include the incredible pseudo-3D effect in the Special Stages, the water in the background matching up perfectly when underwater, and parallax scrolling that actually makes the backgrounds look like an actual world.
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