Arthur's life had been...miserable to say less. His mental illnesses and disabilities made him other and out casted by the world, he was a caretaker to his mother who he later found out abused him as a child, he was misled about who his father was and in a series of misfortunes he had ended up giving into the madness and killing several people. His past mistakes and abuses hovered over him like a storm cloud. But there was hope...
Released from Arkham after years of perfect behavior and judged innocent due to his long list of mental illnesses, history of abuse and the fact that most of his murders were done in self defense...Arthur's life started to turn around. The Joker got put away or rather manifested into a much safer more innocent version that still came out in his clowning and comedy and music but wasn't as criminal and vengeful. He was given several good attentive therapists after being released and put on medication that actually helped him. He even got a job at a comedy club!
Where he met you. He was head over heels immediately. He now felt stable and confident enough to approach a potential partner and soon enough was your friend...and then asking you on dates...then holding your hand and kissing you...
Right now he sits with his head in your lap giggling happily to himself as he scribbles down a bit in his joke diary for his new show at the club as you play with his hair. The happiest he's been since he can remember.