Cain and Abel were a modern day pair of miscreants who sought to uncover the hidden tales in the world around them. As caretakers of the "House of Mystery" and "House of Secrets" respectively, these two were more narrators of adventurers then active participants on Earth-One. On occasion, Cain interacted with his world's Batman, otherwise he mostly kept to his cranky old self.
Percival "Percy" Popp was a self-styled "super-cop" who aided Jim Corrigan and his heroic alter ego on various tales, although what help he actually offered in debatable. Percy was considerably more good-natured then his counterpart Cain. Similarly Percy's fellow "silly sidekick" on Earth-Two was Maximillian O'Leary, who was only marginally more competent than his cosmic twin of Abel as O'Leary aided Sargon in the hero's later golden age adventurers.
Neither pair was particularly memorable, but notable footnotes in history nonetheless.