Originally Posted by Mistah K88
Thirded, Joker's a big enough character who could stand on his own. Plus here he was only starting out, Harley would come in much later in his career when Joker has a prescence in Gotham.
Yeah, it wasn't needed at all.
I think it would be interesting if the next Joker on film (an already established version who has a long history with Batman) has Harley, though.