Lorenzo Semple Jr. gives a subtle backstory for the Joker: when Batman shows the Joker's mugshot to the kids, the Joker is wearing a normal suit, and there is a reference to him being a "master of disguise", leading one to believe this version wears clown makeup (not unlike Heath Ledger's version in The Dark Knight), instead of having his skin discolored by chemicals (as was the original comics character and the Jack Nicholson version in Tim Burton's 1989 film).
In November 1965, Semple concocted a new villain named The One-Armed Bandit, "whose peculiar kick is gimmicked coin machines of all sorts".
The idea ultimately wound up in these episodes with Joker in charge of The One Armed Bandit Novelty Company and vending machines that churned out silver dollars, quarters, answer sheets to exams, and knockout gas.
He and his henchmen snag Batman and Robin with one of the rigged vending machines which, instead of giving out silver dollars, locks them in shackles and emits sleeping gas.
Batman and Robin are transferred to the inside of a moving van, where they are strapped to electric chairs; on the wall is a slot machine, which when activated will win them their freedom and $50,000 cash with 3 liberty bells; just their freedom with 3 oranges, and instant and inescapable 50,000 lethal volts of electricity with 3 lemons, automatically on the last lemon.