As a huge fan of "Batman: The Animated Series" I have always loved Harley Quinn. This character was actually invented in the cartoon first and then later became a fixture of the "comic book world",
She is also about to be depicted in a new live-action movie, Suicide Squad, which I think is going to introduce her into a larger mass audience who is sort of unfamiliar with her origins.
So, this is the reason I chose to feature this "character history" video from Comic Explained. It gives a nice intro to her... Enjoy!