These characters are antagonists that are not very story-centric, but still battle the heroes.
- As a last resort, Eggman manufactured this to catch Sonic unprepared. This, except for the power plant embedded in its head, is a mere stuffed animal, whose meager form nevertheless exhibits considerable ability in races due to its lightweight design. Still, it is also able to float in the air for a long time.
A floating doll-like robot from Sonic R, made in the likeness of Tails.
- The Cameo: In Sonic and the Black Knight, it makes a cameo appearance in the fan art section.
- Chuck Cunningham Syndrome: Never appeared again after Sonic R, though dummy dolls of Tails did appear in Sonic Adventure. That didn't stop fans from making creepypasta about it. Though, it does gain a successor of sorts in Sonic Mania, in the form of the Amy Doll.
- Evil Knockoff: A hastily made attempt by Eggman to provide a counterpart to Tails as Metal Sonic was to Sonic.
- Flat Character: Has no personality beyond "doll of Tails". Justified as it's not even a robot, but a ragdoll with a floating mechanism slapped onto it.
- Joke Character: It was made by Eggman in a hurry, and it shows. Tails Doll has poor handling, average acceleration and average top speed. He is the slowest character in the game, but he can glide over water better then most of his metal allies, and he has a strange floating ability as his "air action", allowing him to remain airborne longer than the real Tails can.
- Mecha-Mook: Barely even meets the qualification, since the only mechanical part of it is its floating mechanism, and the rest of it is a crude ragdoll.
- No Mouth: It's a ragdoll with a floating mechanism, so it doesn't have or even need a speaking function.
- Power Floats: It's sole ability is to float through the air.
- The Psycho Rangers: Along with Metal Sonic and Metal Knuckles, it serves as part of an evil trio counterpart to the main heroes.
A robot who is sent to capture a Flicky in possession of a Chaos Emerald. As Amy protects that bird, he goes after her too. He's also the first of the E-Series, his code-name being E-100 Alpha.
- Achilles' Heel: There's a battery in his head that acts as his weak point.
- Arc Villain: He's The Heavy of Amy's story in Sonic Adventure.
- Climax Boss: He's this in Amy's story, along with being the only boss she must fight.
- The Heavy: of Amy's story in Sonic Adventure
- Hoist by His Own Petard: The electric barrier in his boss fight is to, presumably, make it so Amy doesn't escape again. That said, it's integral when it comes to killing him.
- Killed Off for Real: He blows up at the end of his boss fight.
- Killer Robot: He's a psycho robot with no common sense other than completing his objective.
- My Hero Zero: His name is ZERO and he would be if he's an ally, he is an ally to Dr. Robotnik.
- Primal Chest-Pound: A trait of his that emphasizes that he's a cruder model than the rest of the E-series.
- Psycho Prototype: Said to be one to Beta, as he is given the codename E-100α or E-100 Alpha on the official websites.
- Puzzle Boss: Knock him into the electrified fence to attack him.
- Super-Persistent Predator: Amy must avoid him in every level. His tenacity even after his target has been obtained and is no longer of use to Eggman gets him killed.
- Unexplained Recovery: Despite being blown up by the end of Sonic Adventure, he reappears in the Special Stages of Sonic Advance 2 as a hazard.
- Too Dumb to Live: He continues to chase Amy and attack Birdie even after the Chaos Emerald in the latter's locket is removed, knocking down Birdie's parents/the recently-freed batteries of Beta and Gamma as well. Amy reaches her Rage Breaking Point as result and finally decides to fight back, killing him.
- Unwilling Roboticization: Averted. He is run on batteries, not an animal.
A robot in the E-Series made by Dr. Eggman. The first and final boss for Gamma.
- Book-Ends: He's the first and the last boss (albeit upgraded) in Gamma's storyline.
- Breakable Weapons: You can destroy Beta's homing missiles with Gamma's cannon.
- Climax Boss: He's the last E-series robot to be destroyed, besides Gamma.
- Cyber Cyclops: He's this when being upgraded.
- Kill Sat: One of his attacks. He is invincible during said attack.
- Mutual Kill: With Gamma.
- Painful Transformation: While it's never specifically shown whether or not Beta could feel pain, Gamma's reaction to seeing his brother's in-progress transformation would imply this is the case.
- Parrying Bullets: Deflects Gamma's shots using his arms. As a result, he can only be attacked from behind.
- Psycho Prototype: To Gamma. He may have been the stronger of the two, but he doesn't take being junked by Eggman in favor of his inferior successor very well.
- Tactical Suicide Boss: Unlike the other E-100 series robots that Gamma faces, his Mark II form cannot be defeated by simply continuously locking on and firing on him. He is only vulnerable when he attempts to charge at Gamma and misses.
- Taking You with Me: After being defeated, he, apparently fatally, shoots Gamma one last time before exploding, but ultimately that's exactly what Gamma wants.
- Unwilling Roboticization: He's powered by a Flicky, one of Birdie's parents along with the Flicky housed in Gamma.
- We Can Rebuild Him: Was rebuilt as E-101 Mark II, after being defeated by Gamma the first time around.
- Wolverine Claws: Mostly just for show (though he does use them to deflect Gamma's shots), but there is one attack where he uses them. That attack is when he's vulnerable.
One of Eggman's E-series robots, decommissioned and abandoned by Eggman after his failure to procure Froggy. The first target on Gamma's list in Sonic Adventure, found in Windy Hill.
- Killed Off for Real: By Gamma to release the animal inside.
Another decommissioned E-series robot on Gamma's list, located in Red Mountain.
- Killed Off for Real: By Gamma to release the animal inside.
Yet another E-series robot on Gamma's list. This one eventually became the defense system for the Egg Carrier and was housed within its Hot Shelter.
- Easter Egg: He's partially built out of Sega Dreamcasts, which you can see if you look closely at his model.
- Killed Off for Real: Once again, by Gamma to release the animal inside.
- Purple Is Powerful: He's the most powerful member of the E-Series tasked with retrieving Froggy, though it's unknown whether he held this title prior to receiving a massive upgrade following his decommissioning.
The supposed leader of the boos that inexplicably appear a lot in Sonic Adventure 2.
- Bedsheet Ghost: Less so than the normal boos, but still somewhat.
- Breath Weapon: He does this after finishing throwing fireballs.
- Evil Laugh: He lets a few of these, especially when he attacks the character.
- Fireballs: Another of his abilities is throwing blue fireballs at the character.
- Giant Space Flea from Nowhere: Just like the other boos. He kind of just shows up and fights Knuckles.
- Jump Scare: In the beginning stages of the fight, you can run fast enough to approach his back before intended. However, instead of actually reaching it, he turns around and rushes at you, which can be a surprise.
- King Mook: Of the boos.
- Pokémon Speak: In the Sonic Runners Halloween Event, he speaks by saying "Boo".
- The Unintelligible: He talks in this manner in his debut.
A giant stone golem robot controlled by Eggman, who is forced to destroy it in Sonic Adventure 2 after it goes berserk following a failed attempt to stop Sonic from progressing through his desert base. A different version of it appears in Sonic & Knuckles, which Eggman controls directly via his Egg Mobile.
A robot created by Eggman's front company MeteoTech which serves as the main antagonist of Sonic Riders: Zero Gravity. It went out of control when it was possessed by one of the Arks of the Cosmos.
- Big Bad: Of Zero Gravity.
- Colony Drop: Master Core: ABIS can toss meteors.
- Final Boss: Of Zero Gravity. Hell, it's the only real boss of the game.
- Generic Doomsday Villain: SCR-HD doesn't really have any real reason for its actions. Justified in that it's a robot so it doesn't have much in the way of personality, and it's under the influence of the Ark of the Cosmos.
- Gravity Master: Thanks to the Arks of the Cosmos.
- Hoist by His Own Petard: He ends up sucked into the black hole he created.
- Humongous Mecha: Master Core: ABIS.
- King Mook: Of the mass-produced SCR-GP robots. The only difference in appearance is SCR-HD has two slanted blue eyes, while the SCR-GPs have a single red eye.
- Meaningful Name: Master Core: ABIS. It's the core of Astral Babylon and it's creating a black hole, or abyss.
- Omnicidal Maniac: After finding all five Arks of the Cosmos, it merged with Astral Babylon's core unit and created a black hole to destroy the planet.
- One-Winged Angel: Master Core: ABIS a Fusion Dance with it and Astral Babylon's core unit.
The primary antagonist of Sonic and the Black Knight, who was supposed to be the benevolent ruler of the world of Camelot, but became corrupted, ruling the kingdom with an iron fist.
- Artificial Human: According to Merlina, he was an "illusion" (heavily implied to be a magical creation) made by Merlin in order to give the kingdom a savior.
- BFS: His sword, the Deathcalibur, which is almost as big as he is and is actually produced by the Scabbard of Excalibur itself.
- Black Knight: He is the titular Black Knight, though his armor is actually a dark gold.
- The Corruption: He was corrupted by the Scabbard of Excalibur.
- Disc-One Final Boss: Nope, he's not the Final Boss or even the main villain. That would be Merlina.
- Evil Laugh: Can do this in the multiplayer mode.
- FaceHeel Turn: It's implied he was a just ruler in the past before being corrupted by immortality.
- Flight: His horse can fly.
- "Get Back Here!" Boss: How his boss fight plays out. Ironically, he says to Sonic, "It looks like there's only one thing you're good at: Running away."
- Glowing Eyes of Doom: It's the only thing visible underneath that armor.
- No Body Left Behind: Vanishes like one of the Knights of the Underworld upon death, which leaves Sonic shocked.
- Not Worth Killing: His initial reaction to Sonic after their first fight.
- Oh, Crap!: When Sonic nullifies the scabbard's power and leaves him vulnerable, he's left in disbelief before Sonic cuts him down.
- Playing with Fire: He'll unleash balls of crimson energy that heavily resemble flames at Sonic. Deflecting them back at him will both fill the Soul Gauge and slow him down.
- Shock and Awe: During their second battle, he unleashes pink electrical arcs from his sword to catch Sonic off-guard. He performs a similar move as an AOE in multiplayer.
- Tin Tyrant: Decked out from head to toe in so much armor it's amazing he's even able to stand up properly.
- With Great Power Comes Great Insanity: It's stated that King Arthur turned evil due to Excalibur's scabbard of immortality.
The progenitor of the Wisps and the creator of Planet Wisp who was corrupted, presumably by Eggman's processes, into a dark monstrosity. Fortunately, after being defeated in the DS version of Sonic Colors, she is returned to her normal self and returns to Planet Wisp with most of the Wisps.
- Beat the Curse Out of Him: She must be defeated by Super Sonic to restore her from her corrupted state.
- The Cameo: Mother Wisp, in Sonic Runners and in Team Sonic Racing.
- The Corruption: She's been corrupted into a Nega-Wisp.
- Cyclops: As Nega-Mother Wisp, she has one eye, on a stalk.
- Dark Is Evil: The only Nega-Wisp ever shown to be truly malevolent.
- Eldritch Abomination: A corrupted tentacled alien monstrosity with two long arms that are tipped with mouths.
- Extra Eyes: Mother Wisp has three eyes.
- Eye Beams: Uses them frequently.
- Giant Space Flea from Nowhere: She has absolutely no buildup or foreshadowing to her appearance, simply showing up after Eggman has been defeated and the Chaos Emeralds obtained.
- Go for the Eye: Ramming into her eye is the only way to permanently damage her.
- Pink Means Feminine: Mother Wisp has pink skin, obviously as the mother of the Wisps.
- Purple Is Powerful: As a Nega-Wisp, she has a purple color. She's also the strongest of them all.
- Shows Damage: The petals on her eyestalk fall off as she takes damage.
- Starfish Aliens: Mother Wisp is basically a giant pink space jellyfish.
- True Final Boss: Of the DS version of Sonic Colors, battled as Super Sonic after obtaining all the Chaos Emeralds and beating Eggman.