You know, I think the problem with "Joker" (and thus why I can finally see why people say the story line is just 'ok'), is that nobody, it seems, has ever thought to do a backstory on this character! He, basically, just appears from nowhere! It seems to me Phillips has tried a logical extension as to the current status of the character, but there's only so much of unlucky 'Arthur Fleck' the audience can take. I mean, how far back do you go...? Therefore, I think the hints were enough at this stage with more exploration to come, perhaps with 'Professor Jonathan Crane' as a side step whilst Margot Robbie continues to destroy 'Dr Harleen Quinzel' on screen?