I've written something like this to people several times in comments, so decided to make a journal about it as I continue to see the confusion.


It was the original manual of the very first Genesis Sonic game were they first introduced the name Dr. Ivo Robotnik as a translation to Dr. Eggman as it's what Japan as always called the guy.
Adventures of Sonic the Hedgehog followed that name and I think it's been the only time I've ever -heard- that name being said by Robotnik himself. "I, Dr. Ivo R(rr)obotnik!"(You know how the guy loved to roll his Rs) SatAM Introduced the name "Julian", though it never did mention the Kintobor.
"The name is no longer Julian. From this day forward, I am...Robotnik!"

It was later that the comics mentioned 'The House of Ivo' and the Kintobor last name spelled backwards as being the origin for the surname Robotnik.

Eggman stayed Eggman until they made Sonic Adventure 1, as they wanted to bring the american and japanese fans together they made Eggman introduce himself as Robotnik:
"I am Dr.Robotnik! The greatest, scientific genious of the world!"
But kept Eggman as a nickname first given to him by Sonic's crew to mock him:
"Whatever you say, -Eggman-!"
To which he reacted rather upset.
After the game's hit and revival of a fandom the released the dubbed version of Sonic OVA (Sonic The Movie) where Eggman was once again translated to Dr. Robotnik and Eggmanland to Robotnikland. His robot, Metal Robotnik was originally called Dark Eggman aswell.

I suppose, America wouldn't take the guy seriously with a name like that. I know I used to hate it myself...

But in Sonic Adventure 2, however, even while they used the name Robotnik as a family last name (Gerald Robotnik, Maria Robotnik), he used Eggman in the screen while he threatened the world. "Join the Eggman Empire!" and introduced himself as Dr. Eggman several times.
This was all to make things less confusing for the fans, since from that moment on Eggman has simply been Eggman. The comics now use the names interchangeably as they still have fans from both sides but you will still see someone asking, every now and then "What's his real name? Robotnik or Eggman?"

So, are they one and the same? Is there a difference? Oh, yes, there are many. Do not make the common mistake of thinking of them as the same character because they are not. Yes, they are Sonic's antagonist and they all want power and taking over the world and love robotics and creating havoc and obsess about the same blue Hedgehog, but they are still not one and the same.

Dr. Eggman (Doctaru Egguman):
The original, the one from Japan, the one in Sonic X, the current games and Archie comics post #76 is Eggman, even if he's called Robotnik and even Ivo. He was born(created) as Eggman and that's the name to tell him apart. His goals are to always be after the Chaos Emeralds or any other source of power from the planet, created an army of robots as well as one big nasty one and go and take over the world and take Sonic down with it too. Or does he really?
He IS power hungry and he is a megalomaniac and loves what he does, but he probably loves it a little too much. He never puts too much effort in truly finishing off Sonic or destroying too much. Perhaps he doesn't want the fun to end as frustrating as it can be to continue "losing". Unless he wants to.
Characteristic traits: Round head, wears glasses, bushy brown mustache. Cartoony version has no freaking jaw, he was redesigned in Next Gen to be more human like and so gained a jaw, neck and *cough* crotch. Wears a red coat with white lines and yellow buttons/squares/bolts on his chest over a skin tight black overall. White gloves and black boots with metal details. His NG redesign sported light blue eyes.
He had henchmen for the first time in Sonic X. Two robots called ocoe and Decoe as well as some weird thing calle Bokkun. I'm not completely sure if the guy's a robot, he looks a lot more like a Chao or some alien species... I go with the former.
In the game Sonic Unleashed Eggman has a robot that's part of his ship as an assistant of sorts, as well as comic relief.
His voice actor was the very awesome Deem Bristow, who sadly passed away in 2005. His last Sonic game being Sonic Advance 3. The current Eggman VA is Mike Pollock. Each game the character a very differnt tome. The former a more badass, intimidating one while the latter a more comical one.


Dr. Ivo Robotnik (Doctaru Eebo Robotonikku[oh I adore that name]):
Pingas! Oh, yes, that's the one. Damn the internet for making him even more comical than he already was. He wanted to turn the world into....uhh....whatever he came up with at the moment. He just wanted to prove to everyone that he was a genius and his word, as absurd as it was, was law. The only one with a mother(if the thing can be called that) and also the only one who had managed to have a sort of Super form by gathering all power gems from his world. Never taken seriously, much less by Sonic himself but he was the ONLY incarnation who actually managed to grab Sonic at one point and strangle him. He could have killed him off right then and there, but he just tossed him in a cell, just to prove his inventions were awesome.
Characteristic traits: Egg-shaped head, buck teeth. Black eyes with red pupils, has an iris. His mustache is brown and looks like a brush on each end. He wears a skin tight overall divided by a yellow cross symbol with a circle on his belly. The upper half is red while the lower one is black. Sometimes sports a yellow cape reminiscent of the original Eggman who had one too. His gloves are grey with stud on them. Grey and red boots. His henchemen are Grounder, Scratch and Coconut as well as many other minor robots he makes that get destroyed every episode.
(personal note: He was adorable as a baby, looked like a water drop )
His voice actor was Long John Baldry, deseased also in 2005.


Dr. Julian Robotnik(Jurian Robotonikku):
My main guy. :3
He is the ONLY one who managed to actually conquer the world, most of it anyway, and the rest are barred wastelands and random nature areas here and there. His goals are to expand his territory of industrialization and turn every living thing into metal and slaves to speed up the process. He's the antagonist of the most darkest and serious Sonic cartoon. Dr. Julian Robotnik it's the ONLY incarnation to have ever made Sonic the Hedgehog cry and be the only one who has Sonic expressed how he hates him instead of just the other way around.
He also has a pet chicken called Cluck. His henchman or lackey is Snively, who has a story of his own as well as differences from the cartoon and comic incarnations but he's not my specialty. He is Julian's nephew who's been with him since the beginning and though at first he seemed to have respect for him harbors a deep loathing for his bad treatment eventually and desires to get rid of him and take his place. Something that Robotnik himself probably knows but doesn't think of it to be that big a threat.
Characteristic traits: are black eyes with red pupils, round metallic bulbs for ears and a left robotic arm. Sports pretty much the same attire as Ivo Robotnik, adding large pointy pauldrons on his shoulders and a longer cape. His head is also egg-shaped but more round. Loves showing teeth as he actually has a rather large jaw. His mustache is the most modest of all, being thinner than the other incarnations and colored orange. Grey gloves and black boots with Red toe and heel. He's shown to have quite an variety of attributes hidden on his body. His metallic arm can fire lasers from his fingertips. His boots activate boosters by either smacking their heels together or pressing a hidden button on his "belt".
His grudge against Sonic began when a future Sonic traveled to the past and caused him to trip and have his arm robotiziced by his own machine. Also only incarnation to have achieved world domination long before Sonic became his enemy.
Voiced by the very awesome Jim Cummings who really does make the character what he is.
Archie comics added a larger arsenal of weapons to his arm including a missile launcher, a shield and a much lager and stronger laser blast. In Archie comics it seems his father was the one called Ivo, or either as a family name as he came from "The house of Ivo". There he had a brother named Colin who was Snively's(Colin Jr.) father.

This incarnation appears also in Sonic Underground, a more comical cartoon I can speak very little of because I barely saw it, but was voiced then by Gary Chalk(Optimus Prime and Grounder). He was seemingly less threatening though he also had taken control of most of the planet and was still turning flesh into machine.


Sooo, did I forget anything?
I'm surprised at my own memory! Most of this things I learned years ago when I did nothing but search for "Sonic the Hedgehog" and "Dr. Robotnik" on Google~