Dr. Robotnik

"Self-proclaimed evil genius scientist and megalomaniac. He's always trying to take over the world but a certain blue hedgehog keeps getting in the way..."

- Sonic Mania's description manual.

Dr. Ivo Robotnik sometimes nicknamed as Dr. Eggman is the main antagonist and has a lot of hatred for Sonic and his friends for ages. He keeps inventing new machines with his incredible 300 IQ rate, but he always fails to his foes, yet, he never stands back. He will never surrender in beating the hedgehog.

Sonic Mania
The Eggman has been defeated again by the hedgehog and his companion, but after his defeat, he detects a powerful source of energy located in Angel Island, which allows him to send his Egg-Robos to search for the power. He then finds the power source in Green Hill, but was soon battled by the heroes. After his demise once again, he meets the upgraded robot squad, who have now become the so-called "Hard Boiled Heavies." He picks up the Phantom Ruby (the energy source) and uses to send the heroes to somewhere else.

Later, Robotnik uses the gem to restore the Little Planet to it's mechanical state and also builds the Titanic Monarch on it. He also tries to defeat the group multiple times later on, yet still resulting in failure. He'd use the ruby every time his plan starts going downhill.

Almost at the end of his scheme, Sonic and co. chase down Robotnik into his new jewel-powered Phantom Egg whilst the Phantom Heavies battle them as well. Although defeated as usual, the Phantom Ruby sent them to Egg Reverie Zone, where the Phantom King stole the gem and goes into battle with Robotnik. Sonic, now in his super state, defeats both villains.

Sonic Mania Plus
In the aftermath, Robotnik attacks Sonic and the rest with the Death Egg Robot. He is once again in defeat and comes across the revived group of Egg-Robos, who stole the ruby again. Robotnik does his same tactic and same plot once again. But in one change, the Phantom Ruby activated, unleashing it's power to act as a black hole. Robotnik tries to escape in his jet sled, but gets chased by the heroes in their mighty super forms. He plummets in the vacuum of doom by the group, whilst his enemies win.

Sonic Returns
Sonic is back on Angel Island and sees that his greatest rival is back at it again, kidnapping the peaceful Flickies. When Sonic steps on the spring, he eventually gets kicked off of the capsule and lands in a trap. This is all set up by the genius Robotnik, who faked the capsule to be a bomb. Just as Robotnik was about to leave Sonic in an explosion, the hedgehog bribes him with an emerald. Sonic tricks him into falling in his own trap. Robotnik tries to snatch the emerald but Sonic kicks his foot and frees himself. Robotnik tries to make him feel guilty, which works, but Robotnik's evil device falls out of his pocket. Sonic inspects the device, which reads that Robotnik has four emeralds and plans to take the others as well. Sonic punches the bomb to a rate of five seconds before exploding and leaves Robotnik in the bombing area.

Sonic And Tails
When the device is handed over to Tails, it scans that a white emerald is near them, short after, they feel a quake trembling from the forests of the island and see a smoke cloud emitting from said location. It is in fact Robotnik drilling in the ground with his drilling machine. Sonic stands and runs behind Robotnik, but Robotnik hits Sonic with one of his drills. He continues his search, but he feels turbulence on his machine, coming from both sides. Sonic and Tails bump into the machine multiple times before Robotnik almost plants a drill through Sonic. Tails saves Sonic. Robotnik did not see this action and cheers for mere seconds, until realizing he missed. In the air, he sees Sonic and Tails making a special finisher on Robotnik's machine, which blasts him off into the beach.

There, Robotnik receives a video from a spy cam, controlled by a Monkey Dude. It shows Knuckles carrying around the Master Emerald, which Robotnik would love to snatch. He uses the Tornado bi-plane to get to the location.

& Knuckles
Whilst Knuckles got distracted by a trio of Rhinobots, Robotnik successfully captures the Master Emerald, which Knuckles believes to be Sonic and his friend, judging by the same plane these heroes use.

Mighty And Ray
When Mighty and Ray charge upon Robotnik's base along with the other noble protectors of Angel Island, Robotnik watches in said laboratory, viewing his enemies come closer and closer. But he puts on a smile on his face for what's to come.

Metal Mayhem
In the laboratory, Robotnik rises from underneath the floor, juggling the emeralds from hand to hand whilst maniacally laughing. The emeralds then pass on to his creation, Metal Sonic, who absorbs the emeralds. As Metal and the team start to charge into battle, Robotnik watches from a distance, admiring the combat of the replica of Sonic the Hedgehog. Miles and Sonic have trapped Metal Sonic as he was about to attack, Robotnik stands perplexed, but his badnik obtains the Master Emerald, which he cheers on with. Knuckles enters the scene, punching Metal Sonic into Robotnik and shooting both villains off into the forests of the island.

From A. Rose
The two bump into a tree and fall on the ground. Robotnik angrily stands up and kicks Metal Sonic twice for him to respond, but no answer comes out of the robot. Robotnik furiously leaves the area.

Later, someone rings the doorbell. He opens the door and sees an injured Metal Sonic on his doorstep with a ribbon on his head and a flower in his hand. He skeptically looks around and takes Metal Sonic inside the lab.

Appearance
Robotnik is a big rounded man with a large mustache under his pointy nose which is also under his pince-nez glasses. Hear wears a red shirt with a yellow cape with an big collar and a long black pants with gray/white buckles on it. The phrase "Eggman" makes sense when you'd look at his bald and shiny yet small head.

Trivia

 * Dr. Robotnik is often called by his nickname "Eggman."
 * Dr. Robotnik and Tails both have brilliant IQs.
 * Metal Sonic is one of his creations he is the most proud of. He doesn't show this at all times.
 * The Hard Boiled Heavies are Egg-Robos who once obeyed him. Due to his finding of the Phantom Ruby, they no longer do so.