The Mad Thinker is a fictional character, a supervillain in the Marvel Comics Universe. He is a genius specializing in evil robotics and usually comes up with very elaborate infallible devious plans that unfold like clockwork. The Mad Thinker was introduced by Stan Lee and Jack Kirby in Fantastic Four #15 (June 1963). His real name and origin has never been revealed.
Despite being a long and recurring opponent of the Fantastic Four he does have some notable limits, for example when Wizard tried to experiment on Franklin Richards the Mad Thinker was repulsed, not wishing to harm a child : to this end he even teamed up with the Thing to save Franklin from Wizard.