Molly was the first Harlequin. She was the secretary of Alan Scott also know as Green Lantern of the JSA. She became a villain to get closer to Green Lantern using glasses that let her cast illusions and hypnotize people as well as a mandolin that she uses as a weapon. After the War had ended she later reformed and became an undercover agent for the FBI. When Alan's children, Jennie-Lynn and Todd (Jade and Obsidian) resurfaced, as did Molly and she finally told Alan about her secretive past and they had a long awaited marriage.
Harlequin II was one of the many names that Duela Dent used.
Granddaughter of the original Manhunter, Dan Richards, Marcie Cooper joined the alien Manhunters who had a plot to take over Earth. She got a job at a radio station KGLX, in Gotham City, with Molly Scott, the first Harlequin. Marcie started dating Northwind and later Obsidian, both members of prodigal heroes Infinity Inc., and later started to infiltrate them. Stealing Molly's illusion casting glasses she became the third Harlequin and betrayed the Manhunters, attempted to recruit Obsidian to the Manhunter's cause, failing she killed her grandfather for betrying the Manhunters. She then tried to destroy Infinity Inc. and joined Injustice, Unlimited. She tricked Solomon Grundy into touching Mr. Bones's hand to Skyman's face, killing Skyman. Realizing what he had done, a horrified and angry Solomon Grundy killed Marcie.
A so-far-unnamed young woman appeared in Green Lantern Corps Quarterly claiming she was destined to be the new Harlequin and marry Alan Scott.
Harlequin has appeared in the Elseworlds story called Kingdom Come. She apparently has no ties to the other Harlequins and has modeled herself after the Joker and his crazy antics.
Her primary tool was her glasses (Later explained as a gift from the Manhunters as one of their agents) which 1) Projected realistic three-dimensional holograms,2) Fire energy blasts, and 3) In recent years, enabled an aged Harlequin to "maintain" the physical vitality of her youth's athleticism.
Her secondary tool is a mandolin with an extending handle which she uses as a defensive weapon. (Especially against the Golden Age Green Lantern due to his weakness to its wooden construction