The first live-action iteration of The Joker, played by Cesar Romero in 1966’s Batman television series, is a far darker character than viewers may think. The classic Batman TV series is famous for being a more campy and comedic take on the Dark Knight's mythos among the many live-action versions of Batman, with the show influencing the collective perception of Batman and his supporting cast for decades, until the 1989 film of the same name presented a darker and more serious mainstream iteration. Despite typically being portrayed as more of a prankster than a murderous crime boss, Romero’s Joker committed numerous heinous acts off-screen.

https://screenrant.com/batman-cesar-romero-joker-darker-than-you-remember/