He always believed that the criminally insane were merely misunderstood and his controversial views were best expressed in his book I'm Sane and So Are You. His views were modified somewhat after being held hostage by the Riddler live on television, though he continued his work with Gotham's colourful criminals for some years until he met an unpleasant end, eaten by Killer Croc.
Joker's Last Laugh
It is Simpson's skeleton that Batman, Spoiler, and Huntress find in Killer Croc's Lair and believe it's Tim Drakes. (Simpson's body isn't truly identified for a couple of issues later.)
His name references the Simpson and the Flanders family from the TV show on Fox, The Simpsons (1989-Present).