Acrofatic: Much like in previous games, Eggman is still somehow able to keep up with Sonic in terms of speed when the Deadly Six revolt against the Doctor's enslavement.
Action Bomb: The Wii U version has the Black Wisp, a rarely acquirable item. When used, it turns Sonic into a rolling bomb; after a few seconds of use, he automatically explodes, taking out all enemies in range.
Adult Fear: Two of these become quite pronounced as the story progresses:
Your little brother getting kidnapped, with the kidnappers gently informing you that they will do something irreversible to him.
Getting everyone you ever knew and loved in grave danger because of your own mistakes.
Alas, Poor Yorick: Orbot quotes this in response to Cubot losing his body during the Deadly Six's revolt.
Some of the stages are on-rails, in which Sonic is constantly running and cannot stop. In those stages, there are chains of enemies moving with you in places that you must homing attack continually. However, if you - say - hit one of those streams a little too late and end up hitting the last enemy further down than you ought to have, such as just before a pit, the game freezes momentarily to allow the player to see what they're heading into, get their bearings, and avoid panic.
In addition, once you are down to your last life while playing a level, a special "Wing Item Box" appears. Hitting it will automatically teleport you to the next checkpoint, or the end of the level if you've already reached the last checkpoint.
Arc Number: 6. Sonic and Tails travel to Lost Hex, which is made up of hexagonal tiles (which are six-sided), and he must fight the Deadly Six.
Orbot: "If we don't find your friend, can I be your sidekick?" Sonic: "What?! Shut up! What kind of question is that?"
The Atoner: Sonic impulsively kicks the magic conch Eggman was using away without even bothering to find out what it was for, thus allowing the Deadly Six to usurp Eggman's mechs and operations and try to destroy the world. The rest of the game deals with Sonic trying to stop the Six and make up for it.
Sonic: "The whole world's in danger because I did something stupid! Do you have any idea how much that bites?"
Attack of the 50-Foot Whatever: In Lava Mountain Zone 3, Zavok utilizes his "full strength" to grow into a giant, whom you must evade and send exploding platforms into.
Desert Ruins Zone 4, due to a slowly advancing dust devil summoned by Zomom to kill Sonic. It is also the first classically slow auto-scrolling stage since Lava Reef Act 2 in Sonic 3 And Knuckles.
Tropical Coast Zone and Sky Road Zone 3 both have Sonic riding the air currents while engaging with the Deadly Six's fleet of robots.
Backhanded Apology: Sonic makes one in response to Zeena being more concerned about her nails than how she's helping to destroy his world.
Zeena: "The last time we met, you ruined my nail art. Now I have to reapply a whole new coat!" Sonic: "Oh, my gosh, are you serious?! I am so, so sorry." Zeena: "Oh! Well, in that case..." Sonic: "Uh, no. What I meant to say is I am so sorry that you have nothing more important to do in life!"
Badass Grandpa: Master Zik is over a thousand years old and looks his age, but he's still an excellent fighter who can easily take on Sonic.
Badass in Distress: Tails is captured in Silent Forest, and left to be turned into a robot. He manages to hack the machine that would have done so to retain his free will, rescuing himself from the Deadly Six's fox-napping.
Beware the Nice Ones: Sonic actually gets rather antsy with a Zeti after Tails is captured. Of course, given said Zeti is Zor, it doesn't really have much effect.
Big Bad: Dr. Ivo "Eggman" Robotnik. After they usurp Dr. Eggman, the Deadly Six become the main antagonists, only for Eggman to overshadow them in the end when he reveals he was just using Sonic to get rid of them.
Big Bad Duumvirate: The Deadly Six is a group of six Zetis, led by Zavok, who aim to drain the energy from Sonic's world to make themselves grow more powerful.
Big Boo's Haunt: In the Wii U version, Sky Road Zone 4 is haunted by Boom Boos, who serve as invincible obstacles.
Big "NEVER!": This is what Robot Tails yells in response to Zavok's order to destroy Sonic.
Blackout Basement: In the Wii U version, the later parts of Silent Forest Zone 4 has Sonic grabbing pulleys to turn on the lights.
Bleak Level: Nearly the entirety of Lava Mountain has Sonic fighting all the members of the Deadly Six alone, due to Eggman (supposedly) falling to his death, Tails being kidnapped and forcibly turned into a robot, and Amy and Knuckles succumbing to the Deadly Six's energy-draining machine.
Blood Knight: Zazz. Seriously, he loves a good fight more than eating three square meals a day.
Bond Villain Stupidity: Zavok. Instead of personally supervising the roboticization of Tails, he and Zomom just leave him all alone in the lab. Being the Smart Guy he is, Tails successfully modifies the machine he's bound to to his own advantage. See Chekhov's Gun below for other details.
Bonus Stage: The Hidden World, which unlocks after beating the game in the Wii U version.
Boss-Only Level: Lava Mountain. In the Wii U version, Zones 1 and 4 has Sonic fighting Zazz, Zomom, Master Zik, and Dr. Eggman, respectively. In the 3DS version, the entirety of the world has Sonic just fighting all of the Deadly Six, two at a time in respect to the order that they're fought throughout the game, and Dr. Eggman.
Brainwashed and Crazy: The Deadly Six appear to hijack Eggman's Badniks using mind control. Specifically, they can control his mechs because they can innately manipulate electro-magnetic fields.
Broken Ace: The usually high-spirited and unstoppable Sonic becomes increasingly disillusioned as the story progresses, as his recklessness triggers events that seemingly doom his world and kill his friends before his very eyes.
Bubblegloop Swamp: In the Wii U version, Silent Forest Zone 1 has Sonic going through a jungle with harmful mud and invincible crocodile robots.
Build Like an Egyptian: The indoor section of Desert Ruins Zone 1 on the Wii U version, as well as Zone 2 on the 3DS version, has Sonic going through a Egyptian-esque tomb while avoiding giant sandworms (in the case of the Wii U version).
The Casino zone from Frozen Factory heavily takes cues from Casino Night Zone. It even has its pinball tables, slot machine wheels with the same icons, and the "SONIC" and "MILES" signs. However, it has taken efforts to differentiate itself from Casino Night Zone, such as taking on a more purple color scheme.
Cubot's pirate voice has returned.
Sonic calls Eggman "Baldy McNosehair" in one cutscene.
Frozen Factory Zone 4 is callback-o-rama, including the return of the crushers from Metropolis Zone as well as that zone's screws that you must run or spindash on to move up.
The final boss seems to be an upgraded version of the original Death Egg Robot, sporting Eggman's classic design and the aforementioned mech's signature rocket arms.
When you beat Eggman in the last level, there's an explosion in the final mecha's destruction, just like in Colors.
The memetic huge sub sandwich makes a comeback, being taken to the logical conclusion of Zomom noshing on a sandwich probably about twenty feet long.
When Zavok and Zazz decide to taunt Eggman with the world's impending demise and his own failure, he utterly wrecks the wall of ice that they were projecting on. This seems unfeasible, until you remember that Sonic Riders classified him a Power type.
Sonic and Eggman once again join forces to take on Eggman's rebellious allies, but this time, it happens from the get-go rather than a True Final Boss scenario.
When the capsule opened by the Zeti reveals Tails instead of Sonic, Tails is sitting there using one of the Idle Animations Sonic used in Sonic the Hedgehog 2. Specifically, the one where he's drumming his fingers and tapping his foot while lying on the ground.
In Wii U's Silent Forest Act 4, Sonic must hang from switches in the ceiling to turn on the lights, which eventually die out, just like in Sandopolis Act 2 in Sonic 3 & Knuckles.
Cerebus Syndrome: The game starts off light enough with Sonic & Tails doing their usual routine of stopping Eggman, but once the Deadly Six turn on him, things get progressively darker. Tails is kidnapped and nearly turned into a robot under their control, Amy & Knuckles have the life sucked out of them while Sonic helplessly watches, and even Eggman looks like he bites it saving Sonic from Zik, Zazz, and Zomom.
Charged Attack: Aside from being able to lock onto multiple enemies at once, the Homing Attack can also lock onto a single enemy up to six times to do more damage. This is key to beating most bosses quicker and defeating Zavok in Sky Road Zone 4 - hitting him when he's on the edge with the reticule fully "charged" will force him off.
The Charmer: Zavok knows exactly what to say to convince Zeena to attack Sonic.
Chekhov's Gun: Believe it or not, Zomom's giant sandwich, which he forgets on the roboticization machine Tails is tied to. After the Zetis leave him alone, Tails uses one of his tails to grab the toothpick stuck in the sandwich and uses it as a pen on the machine's touch screen to modify the program to his advantage.
Chekhov's Skill: Tails stated that he reprogrammed a supercomputer with a toothpick. Later on, he managed to hack the robotization machine using only Zomon's sandwich toothpick to save his own life.
The Wisps, with the new ones being (Indigo) Asteroid, (Magenta) Rhythm, (Crimson) Eagle, and (Black) Bomb, along with the returning ones like (Yellow) Drill, (Orange) Rocket, (Green) Hover, and (Cyan) Laser.
The 3DS Version also gives us (Red) Burst note From Sonic Colors DS and Generations 3DS, (Gray) Quake, and (Ivory) Lightning.
The Deadly Six: Zavok (red/black), Zazz (pink), Zeena (green), Zik (blue), Zomom (yellow), and Zor (purple/white).
Creepy Shadowed Undereyes: Zazz, Zik, and Zor each have some variation of under-eye shadow, denoting their respective insanity, age, and depression.
In addition to that, there's DLC where Sonic visits the world of, of all things, Yoshi's Island, complete with Yoshi and Mario enemy cameos. (Whether or not this will lead into an official Mario and Sonic platformer is unsure.)
Another piece of DLC has Sonic running around Hyrule as well, dressed in a green hat and tunic and fighting Deku Scrubs, Stalchildren, etc.
Darker and Edgier: Despite the more stylized look and the brighter colors of the game, the dialog is much more harsh in this game, with references to genocide, strangling, and being skinned alive. And let's not forget that Eggman tells the Six that he'll "eat their black hearts" and destroy "everything [they] love".
There's also the scene where Amy and Knuckles have the life sucked out of them.
Despair Event Horizon: SONIC of all people reaches this. Despite continuing on, he's incredibly affected as everyone seemingly drops like flies thanks to his bull-headed stunt that led to the Deadly Six breaking free: his world has been sucked dry of its life-force, Amy and Knuckles seemingly die because of it, Tails has been captured by the villains (and Sonic is also mortified when Zavok tells him that they're going to turn him into a robot), and, for extra measure, he's forced to watch Eggman, Orbot, and Cubot plunge into lava. He almost seems resigned when he sees Tails turned into a cyborg of sorts until he reveals he's still in control and not a robot. Eggman even returns, ready to reclaim his victory, and, at the end, everyone's revived.
Despotism Justifies the Means: When Eggman stands poised with his latest weapon after Sonic defeats the Six, he says that, while it's a pity that the Deadly Six have largely destroyed the world below, at least there's still enough of said world left for him to conquer.
Tails' kidnapping after the first act of Silent Forest is acknowledged by the game when you access some of its features:
In the 3DS version, he is missing from his lab, and text captions for different menu options, which were supposedly spoken by him, are replaced with something more neutral.
In the Wii U version, he is replaced by Cubot in the circus tent minigames.
In the Zelda DLC, if you attempt to use the Black Wisp's Wisp Power to blow up a Gossip Stone, it'll launch into space like a rocket just as how a Gossip Stone would launch into space if you tried to attack it using a bomb in the original Zelda games.
Disney Villain Death: Dr. Eggman falls off a collapsing bridge near the end while saving Sonic, but it's later revealed he had a jetpack to save himself and work on his plans. Then he falls for real at the end, thanks to Sonic removing a part of the jetpack. He somehow survives the fall, but got stuck in a patch of soft dirt and had half of his mustache eaten by a rabbit Also, you get the actual deaths of Zor and Zavok, who are sent falling into the lava.
The Dog Bites Back: After being under Eggman's thumb due to his torturous conch, the Deadly Six waste no time unleashing swift payback once Sonic obliviously gets rid of it.
Double Jump: A more effective one than the double jump in Colors, though Sonic uncurls after using it in the Wii U version, leaving him vulnerable. He stays curled in the 3DS version.
Dream Land: Nightmare Zone, the first DLC in the Wii U version, takes place in Sonic's dream, where he fights the boss Nightmaren from Ni GHTS Into Dreams.
Dropped a Bridge on Him: The Deadly Six all die during gameplay rather than in cutscenes. Zazz, Zomom, and Master Zik are killed off like common enemies. At least Zavok's was a little more climactic, but they don't even show a cutscene of Zavok falling to his doom as they do of Dark Gaia's death.
Dwindling Party: First Tails is kidnapped to be converted to a robot, then Amy & Knuckles seemingly are sucked into the life-draining machine offscreen, and then Eggman sacrifices himself to save Sonic from the Deadly Six. By the time Sonic fights them in Lava Mountain, he's very much alone. Zavok actually mocks Sonic about it in Sky Road Zone 4.
Epileptic Flashing Lights: A glitch found in the second pinball table (where a red ring resides) of Frozen Factory Zone 3, where results causes the entire screen (except the HUD) to flash constantly, and Sonic will be stuck until the timer runs out, the stage is reset, or the game is closed. Caution must be taken, especially if you're epileptic — that is, if you haven't downloaded the patch that fixes this.
Enemy Mine: Sonic and Eggman have to team up to take on the Deadly Six.
Eternal Engine: The Frozen Factory, a Metropolis Zone-esque factory in the frozen part of the Lost Hex.
Even Evil Has Standards: Eggman only wants to borrow the planet's energy to conquer it, and is shocked when he discovers the Deadly Six intend to destroy the world outright.
Evil Is Petty: Zeena cares more about doing her nails and makeup than helping her comrades take down Sonic.
Evil Virtues: Eggman's redeeming aspects are Lampshaded during his team-up with Sonic, even going so far as to put himself in harm's way to save his enemies.
Sonic: "I can't figure you out. One second you're contemplating genocide, and the next, you're saving one of your worst enemies!" Eggman: "I'm a complicated guy."
Eviler Than Thou: The Deadly Six prove to be the greater evil than Eggman after they break free of his control.
Face Palm: Eggman, after Zomom smashes part of his lair's floor to grab a sandwich.
Freeze-Frame Bonus: From the Nintendo Direct "Yoshi's Island Zone" trailer, part of the checkerboard background in Windy Hill is changed, showing the Triforce, hinting at a Zelda-themed DLC level.
Flaying Alive: During their fight, Zazz explicitly threatens to skin Sonic alive.
Floating Continent: The Lost Hex, the domain of the Deadly Six, is a hollowed-out miniature planet floating above Sonic's world.
Forced to Watch: Invoked; while ranting at the Deadly Six for their rebellion, Eggman vows that he will "destroy everything they love and make them watch."
Later in the game, the trope is played straight for Sonic, who's forced to watch Amy and Knuckles die through the Miles Electric and can't do anything but desperately call their names.
Gadgeteer Genius: Taken Up to Eleven with Tails here. He claims that he made a TV set out of paper clips and hacked a supercomputer using nothing but dish soap and a toothpick, and thus repairing the Tornado is as easy as taking a nap for him. He also later manages the impressive feat of kindarobotizing himself.
Gameplay and Story Segregation: The second cutscene is potentially this if you managed to find some non-goal animal capsules from a path alternative to the main one, as the cutscene only makes sense if the goal capsule was the only one opened in that level. Averted in the 3DS version, which the same cutscene only plays when you complete the tutorial level (which, naturally, only has the goal capsule in it).
Genre Throwback: This game aims to capture the look and feel of the classic games, not only by making the art style more stylized, but even extending to the gameplay.
Get Back Here Boss: The final boss battle against Dr. Eggman has Sonic running after Eggman's mech in a section of the Lava Mountain.
Windy Hill. It even has the the checkered cliffs, totem poles, log bridges, and waterfalls of Sonic 1's Green Hill Zone.
Yoshi's Island Zone, the second DLC level in the Wii U version, takes place in a stage reminiscent of the grasslands levels from Yoshi's Island.
Ground Pound: Sonic can perform the Bound Attack by pressing the secondary action button after jumping without targeting an enemy or obstacle. The Grey Wisps in the 3DS version augments it through the Grey Quakes, allowing Sonic to smash otherwise unbreakable blocks and badniks to pieces.
Zavok in Sky Road's last level. He won't go over the edge at the end of his boss fight unless the homing attack reticule locks onto him more than once, resulting in a more powerful shove that'll do him in.
Hidden World Zone 1 in the Wii U version, where there is absolutely no indication that, unlike every other level in the game, you just let the timer run out to complete the level.
Hair Flip: Zeena does this quite often, most prominently shown in response to Zavok's charming.
Hard Levels, Easy Bosses: With some glaring exceptions, compared to the often challenging main levels, the fights with the Deadly Six themselves are simple to beat.
Hollywood Magnetism: The Deadly Six have power over magnetic fields, though here, it's largely used to hack into electronics such as Eggman's badniks and take control of them. Fridge Brilliance here, as it's possible that the badniks aren't really sentient and receive their orders through electromagnetic waves. They could've just made it so that Eggman's waves are blocked and that their waves would come through.
Horned Humanoid: All members of the Deadly Six; most of them have two, Zeena has only one, and Zomom has a crown of five horns.
Hornet Hole: Desert Ruins Zone 2, in the Wii U version, has Sonic running through a series of giant beehives to reach Zomom.
Orbot: "If we don't find your friend, can I be your sidekick?"
Sonic: "What?! Shut up! What kind of question is that?"
Orbot: "I didn't mean anything by it. I just thought it might be better to work for you than Eggman."
Eggman: "Hello, I'm sitting right here, you know."
Sonic: "Orbot, no matter what happens, I won't fail again. I will save Tails."
Orbot: "It's stuff like that that makes me want to be your sidekick. Tails is lucky."
Eggman: "Seriously, I'm right here. I can still hear you."
Invulnerable Knuckles: Subverted. In one cutscene, the Deadly Six taunt Sonic and Eggman via video screen on an ice wall, to which Eggman gets so mad that he punches said ice wall until it shatters. He does injure his hands doing so.
Jerkass Ball: Tails seems to have grabbed it. One noticeable example is when he blames Sonic for trusting Eggman to shut down his extractor more than him.
Jungle Japes: Silent Forest, the forested jungle section of the Lost Hex.
A lot of the zones' BGM shown so far has been noted as to being similar to music from Sonic Unleashed. Considering that Tomoya Ohtani, who did some of the music for Unleashed, is also the composer for Lost World, this is very likely intentional.
Zavok: Your fate is to be destroyed. Why don't you just accept that? Lie down and DIE..
There's also "I long for death's cold embrace" and "one second you're considering genocide..."
Hell, with the Deadly Six's assortment of colorful euphemisms, let's just say the whole game averts this and makes damn well sure you know it.
Nice Job Breaking It, Hero: Sonic kicking away Eggman's magic conch shell, the one thing that kept the Deadly Six under his control, is what led to the Zetis' immediate betrayal and their forced alliance. To drive another nail in, Tails even warned Sonic to stay back because they didn't know what the shell did, but Sonic didn't listen.
No Body Left Behind: Zazz, Zomom, Master Zik, and Zeena all explode after their final battles in Lava Mountain.
When brainstorming ideas on how to defeat the Six, Eggman decides it would be simplest just to blow up the entire Lost Hex and them along with it. Sonic, not entirely comfortable with the idea of killing off an entire planet (full of innocent living things) just to finish off their enemies in as spiteful a way as possible, has some objections to say the least.
Likewise, the Deadly Six decide to take vengeance on Eggman by using his life-draining machine to suck the entire Earth dry.
Nominal Hero: Eggman becomes this after the Deadly Six turn against him, forcing him to work together with Sonic and Tails in saving Earth from destruction so that he can get the Six out of his way and keep one of the places he plans to conquer with iron fists.
Noodle Incident: One has to wonder how Tails was able to make a TV out of paperclips, or reprogram a supercomputer with detergent and a toothpick.
No Sense of Personal Space: Zazz. In his cutscene with Sonic in the Windy Hill pre-boss cutscene, he constantly gets real close to Sonic, mildly startling him.
Obvious Beta: Not to nearly the same extent as Sonic the Hedgehog (2006), but from the amount of tweaks and adjustments to the gameplay that were made by the patch, along with the correction of a few minor glitches, it's clear that the Wii U version wasn't tested as much as it should have been prior to release.
Older Than They Look: The Deadly Six are all over a hundred years old. Even Master Zik, the Zeti that looks the oldest, is well over a thousand years old, and according to one of his quotes in-game, considers being a hundred young ("I feel like I'm a hundred years old again!").
Ominous Owl: The owl robot in Silent Forest Act 2. Downplayed in Silent Forest Act 4 to comical extent, as it's smoking from the inside and has most of its moving parts broken or missing, requiring its owl subordinates to carry it around.
Patchwork Map: The Lost Hex is made up of hexagonal patches of environments like desert, ocean, and volcano with little coherence between them.
Pet the Dog: For all of his evil, Zavok is concerned and respectful to Master Zik, even urging him not to trouble himself with fighting Sonic.
Planet Looters: Eggman's latest machine is designed to drain the life force out of the planet, though it is unstable, so he only intends to drain a little bit at a time. The Deadly Six, however, kick the device into overdrive as part of their revenge on Eggman.
Plot Armor: Cubot and Orbot are somehow immune to the Deadly Six's ability to magnetically hijack electronics. It's likely that the Deadly Six didn't bother controlling them due to them being useless in combat (and pretty much everything else). That, or they aren't controlled via radiowaves because as actual sentient beings, they don't need to gain commands from them like the other badniks.
Prehensile Tail: Tails shows this ability for the first time ever in this game, when he grabs the toothpick stuck in Zomom's sandwich to save himself from being roboticized. (It's long been speculated that his ability to fly relies on this trait, but this is the first time it's been clearly demonstrated.)
Pre-Order Bonus: Downplayed. Pre-ordering the game gives the player 25 extra lives on top of the regular four. Useful, but they can be wasted easily.
Rubber-Band A.I. : Zazz gains super speed just to outrun the faster-than-usual Super Sonic that chased him before the second boss battle with him just so that the scene leading to the boss battle happens normally.
Ruins for Ruins' Sake: The last acts of Silent Forest in both versions has Sonic going through a series of temples to reach Zor.
Zomom: (after being defeated in Lava Mountain Zone 1) Mom's right, I am a failure.
Sequel Hook: Eggman mentions that he'll find the conch and regain control of the Zeti at the end. So the Deadly Six may not be completely gone for good.
Seven Deadly Sins: The Deadly Six: Zazz is Envy, Zomon is Gluttony, Zeena is Vanity, Zik is Pride, Zor is Despair, or maybe Sloth, and Zavok is Wrath, or maybe Avarice. There is no lust, probably because this is a family friendly game.
Shark Tunnel: For the Wii U version, Tropical Coast Zone 3 and Lava Mountain Zone 2 has Sonic rail-grinding through a huge water tunnel while avoiding minecarts and badniks.
Shock and Awe: The Ivory Wisp allows Sonic to attract rings and target enemies in a chain of lightning. The Thunder Shield returns with its usual function of attracting rings and in the 3DS version, allows the player to safely come in contact with electrical rails and Spinas.
The new Indigo Asteroid has an ability very similar to that of the Violet Void (consuming all objects around it and making falls slower).
People who finished the Wii version of Sonic Colors will see obvious recycling of that final boss' attacks in Lost World's final boss' attacks. The Wii U one uses the Laser Wisp attack, and the 3DS one uses the Cube Wisp attack.
Teeth-Clenched Teamwork: Sonic, Tails, and Eggman spend just as much, if not even more, time bickering with and insulting one another as they do actually working together.
Theme Naming: All the Deadly Six have names that start with 'Z': Zavok (Red), Zazz (Magenta), Zeena (Green), Zik (Blue), Zomom (Yellow), and Zor (White). They are also a member of a race called the Zeti.
Eggman, arguably. Especially in the scene where he punches the iceblock that Zavok was projecting his message on to gloat at Eggman.
Tails, who actually tricks the Deadly Six into thinking that he's been robotized, and quickly reprograms Eggman's machine.
Took a Level in Jerkass: Tails. The childlike naivete and humility that defined him in previous titles a smug, self-centered, obnoxious, whiny, and snarky attitude. He had a falling-out with Sonic because he was interested in teaming up with Dr. Eggman to corrale the Deadly Six, even though he was perfectly fine with it before. The worst part is that he never owns up to it at the end of the game.
First, he recklessly charges in and kicks the Cacophonic Conch out of Eggman's hands, completely ignoring Tails' warnings to stay back and not even caring about what it does. As it turns out, said conch was a Restraining Bolt Eggman was using to control the Deadly Six, and Sonic's impulsiveness allows the Deadly Six to turn on Eggman and usurp his plans and operations.
When Sonic, Tails, and Eggman learn that the Deadly Six are using Eggman's life-sucking machine to drain their world dry, Tails immediately states that Sonic's first instinct would be to destroy it, which he doesn't even bother to deny. Eggman quickly calls him out on it and explains that destroying it like that would cause an explosion that would incinerate everything within a hundred miles of ground zero.
In a metaphorical sense, this extends to the gameplay itself. It's much less about speed as it is about puzzles and slower platforming, what with the new controls and level design. There are even stealth sections, like the owl in Silent Forest, and there's a hell of a lot of tight platforming. Going too fast in this game will cause Sonic to die... many, many times.
Under the Sea: Zones 1 and 3 of Tropical Coast, in the 3DS version, has Sonic going through a series of undersea caverns.
At certain points in the game's resident Casino Park level "Frozen Factory Zone 3", the gameplay briefly changes into that of a pinball game. You can even lose a life by draining the "ball"note Sonic himself.
There are several gimmick levels littered throughout the game that are completely different from normal, like having Sonic fly through the sky, controlling a snow-ball, and flying the Tornado.
The 3DS version has its special stages, Sky Road Act 3, and the Quake wisp that all use the accelerometer/gyroscope to control Sonic, which can be not only jarring, but irritating, as the stages are nearly unplayable unless the real-life player has a large amount of space to move around in. This formed the basis for most criticism of the game's special stages, which for all intents and purposes are actually quite easy.
Other gimmicks exist in the 3DS version, like rocket flying and the cannon-aiming boss fight with Zor.
They never explain how Eggman managed to escape from the White Space.
Or how Orbot and Cubot got back from space and found Eggman.
Unhand Them, Villain!: During the opening, Eggman is carrying a container of the animals you rescue in Windy Hill Zone 1 with Sonic & Tails hot on his trail. Sonic demands for Eggman to "Drop the critters" and Eggman does just that.
During Windy Hill Zone 3 (Wii U), the music noticeably changes during sections where Sonic is running through tubes with boulders rolling towards him.
Video Game Cruelty Potential: In Windy Hill, you can find herds of sheep wandering about and grazing, and while Sonic can't hurt them, he can jump on or just bump into them, and it'll knock their fur (and a single ring) right off. Do this enough, and it'll send a whole herd of angry sheep charging after him!
Weaksauce Weakness: The Deadly Six are restrained by a special conch shell that hurts them when Eggman blows it. Unfortunately for Eggman, Sonic's impulsiveness leads him to kicking it away without even bothering to learn what it does.
Wham Episode: After the end of Silent Forest Act 1, when Tails gets captured by a trap of the Deadly Six that was supposed to snag Sonic. This is the moment when Sonic starts getting serious for real.
This exchange after Sonic disposes of the conch Eggman was using on the Deadly Six:
Eggman: "That was a mistake..." Sonic: "Whatever! When is it a mistake to take your toys away?" Eggman: "When it's the only thing keeping six angry Zeti from controlling my mechs, you moronic hedgehog!!"
The trap set for Sonic: he automatically assumes it's full of animals and tries to smash it, instead getting Tails into a mess. Clearly, he didn't learn from his experience in Sandopolis Zone...