Mike Lookinland (Bobby Brady)
From Wikipedia: Mike Lookinland was a TV commercial actor before he was cast in The Brady Bunch, having done around thirty commercials. He has naturally sandy-colored curly hair. Because his hair color did not match Peter’s or Greg’s natural dark brown color, he had to have his hair dyed dark brown and straightened to match. The lights on set though were so hot that his dye job would sometimes run down his face. During the last two seasons of The Brady Bunch, his natural hair color was finally allowed to show.