“"If I weren't insane: I couldn't be so brilliant!"”
— Dreadful Birthday Dear Joker
“"What good is my money? Can I spend it like other people? No! Can I go to movies and ball games? No! The only way I can leave this hideout is in disguise... I'm doomed to a living death... [gets a epiphany] Death!... Now that may be a way out for me... That's it... The Joker must die!"”
— Detective Comics #64 ("The Joker Walks the Last Mile")
“(when asked if he will really reform) "Of course not! My business will go on as usual...the important thing is that I'll be free! The Joker shall die so that he may live again!"”
— Detective Comics #64 ("The Joker Walks the Last Mile")
“(as he is being led to his execution as part of his master plan) "So this is the famous Last Mile, eh? Don't cry, boys...this will hurt me worse than it'll hurt you! Ha! Ha!"”
— Detective Comics #64 ("The Joker Walks the Last Mile")
“"Reclaimed from the dead! All crimes paid for! The slate wiped clean! The Joker is free! Ha! Ha!"”
— Detective Comics #64 ("The Joker Walks the Last Mile")
“"Oh, well...I suppose the Joker's holiday had to end some time!"”
— Detective Comics #64 ("The Joker Walks the Last Mile")

Quotes via Wikiquote (CC BY-SA), each with its original source.