PAUL DINI This award-winning author is the man who truly started it all! Paul Dini is THE creator behind Harley, the mastermind who was struck by divine inspiration which led to the fabulousness that is Harley Quinn. He first wrote her as a one-shot character to perform a service in 'Joker's Favour' based off of a friend he knew in college,  who also served as the inspiration behind her nature and personality. He even drew her very first concept sketch! The more he used and experimented her and developed her character, the more unique Harley became and the more popular until finally we found ourselves with the perky perfection we know today. Basing her on his friend, Arleen Sorkin, no one writes a Harley that is quite so Harley as Paul Dini. Paul Dini's Wikipedia entry - lots of great info!
BRUCE TIMM This is the guy who gave Harley the look we all know and adore! Bruce Timm first conceived Harley's character design, a design which is so *perfectly* Harley and spot-on, it hasn't never been remodelled or adjusted for her various incarnations in the comics or the cartoons (with the exception of Elseworlds and the new The Batman series). Much like Dini's writings, no one draws quite such a quintessential Harley as Bruce Timm. His Harley is eternally sassy, sexy, fun, spirited, cute and loveable. Bruce will forever more be the fella who truly gives Harley her life-spirit thru his artworks, and the flair which says "Harley Quinn"! Bruce Timm's Wikipedia entry - great stuff here!
ARLEEN SORKIN Last but anything from least, we have the beautiful Arleen, the original inspriation behind Harley! The very gal pal of Paul Dini, his friend since college days, this is the woman who has immortalised our beloved HQ through her fantastic and lively voice talents, becoming synonymous with the name Harley Quinn. Arleen is the model for everything about Harley - from her voice, to her looks, to her personality. Arleen IS Harley! She embodies Harley's essence, and brings her to life through her voice talents with warmth, humour, charm and wit. Anyone who's ever seen Arleen perform knows she has Harley's bubbly personality and irrepressible nature. Arleen Sorkin's Wikipedia entry - some fun info!