Just call him Dr. Ivo "The Eggman" Robotnik. Reveal that Dr. Ivo Robotnik is his real name, but his villian name is Eggman, given to him as a running joke by Sonic when he faces him for the first time.
You pretty much loosely ripoff Raimi Spiderman Trilogy's story:
Sonic is Peter Parker, a blue eyes high school kid who is in love with this princess from another world. Silly Peter gets bullied by a bunch of kids from school for that since he has her pictures in his locker. His classmate Miles Morales sees this and interferes with it. They both become best buddies ever since.
Peter is the fastest runner at school which earns him the nickname "Sonic". Both Sonic and Miles were in the running team of their district.
Meanwhile, in the background, you see this military facility where some brilliant scientists are working on cruel experiments, combining Boston Dynamics bots with real animals. The animal is given a computerized brain that can contract muscles of the animal and make it move.
Through the shadows you see a dark figure slither through, slowly taking down guards. Suddenly a fog light points through and you see this black masked vigilante wielding dual Berretta. Shadow. He starts blasting through killing guard after guard. The animal panic and start retaliating, some in their mech form. Explosions ensure and suddenly all animals start running through the door. A few radioactive animals start attacking the soldiers, killing them in a bloodbath. Shadow gets bit. Shooting the hedgehog, he chases it out through the smoke between the debris.
You see Sonic chilling with Miles a few blocks when they hear the explosion. They run towards the sound, right then Sonic gets bit by a radioactive hedgehog, and becomes this blue-furred mutated motherfucker. Oh and his eyes turn green when he gets bit.
Basically he makes this face:
Anyways, they all become these Teenage Mutant Ninja Hedgehogs (or whatever bit them). Then you see a big showdown where they defeat this menacing Boston Dynamics machine. It's feels like the end credit scene but it's just the beginning. You see someone climbing a cliff watching over the battle, and he is on the phone. "Yes... They destroyed it. ... I understand, Doctor". --
......... I'm sure you can picture the rest. It leads to Dr. Robotnik becoming "Eggman".