Batman: The Animated Series sure was one of the best cartoon series ever made and the lovely ladies above are some of the main reasons why.
Fun fact (quoted from wikipedia): Harley Quinn first appeared in the Batman: The Animated Series episode 'Joker's Favor', as what was originally supposed to be the animated equivalent of a walk-on role; a number of police officers were to be taken hostage by someone jumping out of a cake, and it was decided that to have the Joker do so himself would be too bizarre (although he ended up doing so anyway).
Personally I prefer the 'The Batman' version of Poison Ivy but only because of the ingenious relationship between Barbara Gordon and Pamela Isley. (For those who don't know; watch the first two episodes in the third season and see for yourself. If you like it but still want femslash I can recommend [link]).