First Appearance - Detective Comics #168 (February 1951)
The 1st Red Hood - In the original continuity, the man later known as the Joker was a master criminal going by the alias of the Red Hood.While attempting to rob a chemical plant, his men were dispatched and then he was suddenly cornered on a catwalk by Batman. Left with no alternatives, he dove into a catch basin for the chemicals and swam to freedom, surviving because of a special breathing apparatus built into the helmet. The toxins in the vat permanently disfigured him, turning his hair green, his skin white and his lips red. Upon discovering this, he went insane, and became the Joker
The 2nd Red Hood - Jason Todd, one of the Robins, had been murdered by the original Red Hood. When Superboy-Prime alters reality, Jason returns from the grave. Enraged that Batman didn't avenge him, he locates the Joker and robs him of his Red Hood outfit (but not before beating him brutally), and takes up the mantle of the Hood.