Hercule is known as Mr. Satan in the original Japanese version of Dragon Ball Z, however the American version was changed in order to avoid controversy.
He is the reigning World Martial Arts Champion, become so by fairly beating other human fighters, in a time when Goku was not competing. Hercule became rich and famous, which he enjoyed a lot. He boasted endlessly on television about his strength, and that he was the best fighter in the world.
He joined the Android Cell's "Cell Games", and although completely outmatched, never got to fight with Cell anyway. After Gohan defeated Cell, Hercule claimed the credit, which brought him immense fame and fortune as if he saved the world. He was also well respected and trusted.
His daughter, Videl, met the Halfbreed Saiyan Gohan, and she trained with him for the new Martial Arts Championship. Videl daughter marries Gohan, and together they have a child named Pan. Pan is the grandaughter of both Goku and Hercule, and it should be noted that Pan is the most powerful female Saiyan ever, even though she is only one quarter Saiyan.
Hercule is old friends with Majin Buu, and it is this friendship that helped Majin Buu excrete the evil energy that then forms Kid Buu. Majin Buu resists killing Hercule at any cost. Hercule is needed to persuade the people of Earth to give enough energy to form a powerful enough Spirit Bomb that ultimately destroys the evil Kid Buu.
In the early stages of the Majin Buu Saga, Hercule claims yet another World Martial Arts Tournament, given to him by Android 18, after cutting a $20,000,000 zeni deal with her.