Anti-Frustration Features: 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.
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 leaves him to contend with a far more powerful and dangerous evil than Eggman.
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.
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.
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.
Call Back: Several shots from the trailer have a lot of similarity to past Sonic games:
The Flickies have returned, as have all the other tiny cartoon animals.
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.
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.
Cerebus Syndrome: Hoo boy. 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 dark. 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.
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.
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).
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."
There's also the scene where Amy and Knuckles have the life sucked out of them.
Development Gag: The Deadly Six Edition features bosses from NiGHTS Into Dreams. Sonic Xtreme was going to feature bosses designed with the NiGHTS engine, which could be one of the few intentional references to Xtreme('s development).
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. Tragically, this fall costs Eggman his mustache, although he somehow survives the fall.
And then 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 destroys 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.
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.
Gadgeteer Genius/MacGyvering: 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.
Guide Dang It: 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 certainly fits here as well. There is absolutely no indication that you just let the timer run out to complete the level.
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.
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.
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!").
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.
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.
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?"
Theme Naming / A Villain Named Zrg: 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.
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.
Unwilling Roboticisation: Eggman's back to using living animals as organic batteries for his Badniks in this game. Almost completely happens to Tails near the end of the game.
Variable Mix: Background instruments fade out when Sonic dies.
During Windy Hill Zone 3, the music noticeably changes during sections where Sonic is running through tubes with boulders rolling towards him.
Video Game Settings: Unlike previous Sonic games, the entire Zone will not be one same theme, but will instead be a collection of different themes, as well as differing between the 7 locations within the two different versions of the game (Wii U and 3DS).
Green Hill Zone: Windy Hill. It even has the the checkered cliffs, totem poles, log bridges, and waterfalls of Sonic 1's Green Hill Zone.
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 destined to Sonic. This is the moment when Sonic starts getting serious for real.
Zeena: Ugh, why won't you die?! You're like a cockroach with a bad fashion sense!
Wrong Genre Savvy: 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!!"