In the initial universe that spawned a Multiverse, a race of immortal inhabitants journeyed from their native Malthus to planet Oa, in the center of that dimension. A small contingent journeyed to Earth-One to become a leprechaun race there.
Since there was no Oa in other universes, the counterparts of those other worlds known as Malthus would journey as large contingents to the next natural center of their universes, the planets of the humans.
On Earth-Two, a large number of these beings became the leprechauns who encountered Wonder Woman and Green Lantern of those worlds. For the heroine, her acquaintance Moon O'Day was the doppleganger of Fergus, sidekick of Earth-One's Jack O'Lantern. Coincidentally, it was Fergus and his pals who created a lantern which Jack used that was similar to that of the Green Lantern Corps. Other allies of Earth-Two's Wonder Woman were Shappy, Hoppy and Woggle, who were counterparts of the most honored of the Guardians of the Universe, those being Ranakar, Herupa Hando Hu, and Paz Pinder Pol.
One Guardian, Appa Ali Apsa, was assigned to journey with Lantern and his pal Green Arrow in search of understanding humanity. As a result, Appa forsook his allegiance with the Guardians and became a humanoid and mortal. As Old Timer, he was an ally and friend of humanity. His counterpart was Owen Cooley, a leprechaun who believed he was related to Doiby Dickles, the sidekick of Earth-Two's Green Lantern. Although a pest, he had a heart of gold and the pair took him as such. Although initially Alan Scott froze Owen in suspended animation, Cooley was later revived and disappeared afterwards.