A brilliant (and amazingly, not mad) scientist who was responsible for the fateful space flight that exposed Richards, his best friend Ben Grimm, his fiance Sue Storm and her brother Johnny to mutating cosmic rays.
This exposure gave Richards the ability to stretch his body into nearly any shape. He called himself Mr. Fantastic. His co-astronauts also each received a strange superpower as a result of the cosmic rays, and the quartet banded together to fight evil as The Fantastic Four.
Richards' inventions are what keep the FF in those nice blue velour uniforms. Once again, he is a scientist, but he is not mad. He's generally regarded as the paternal figure for the group.
The Fantastic Four and all characters named herein were created by Stan Lee, Jack Kirby, and Marvel Comics.