For almost 20 years now, Dr. Robotnik has seen the fall of many of his machines at the hands (and feet) of one Sonic the Hedgehog. But despite his many feeble attempts to destroy Sega's blue mascot, the guy who turned cute little fuzzy animals into robots never seems to give up.
Robotnik, who was in part based on our 26th President of the United States, Theodore Roosevelt (a more pudgy version, at least), is actually who made Sonic fast (and blue). And the pair were friends until an accident embedded the doc with chaos energy, transforming him into the antagonist we all know of today. Since then he's acquired the "Pinky and the Brain" syndrome, where he tries to take over the world no matter how many times he's unsuccessful in the process. He also apparently has a "Star Wars" fascination, based on the creation of his outer space-floating "Death Egg" in "Sonic 2."
But this robust fellow hasn't spent all of his time being trampled by Sonic and his friends. He was the central character in 1993's "Dr. Robotnik's Mean Bean Machine," a game more in the style of "Tetris" and "Dr. Mario" than a 2D platformer. He's also been a playable character over the years while starring in animated shows and comics.