Here's the breakdown:
* Conrad Veidt played the Joker in the 1940 film serial *Batman*. This was the first live-action portrayal of the character.
* Cesar Romero famously played the Joker in the 1960s Batman TV series, a role he became synonymous with.
* Several other actors have played the Joker in various live-action media since then, including Jack Nicholson, Heath Ledger, Jared Leto, and Joaquin Phoenix.
So, while Romero's Joker may be the most famous, Conrad Veidt was actually the first to bring the character to life on screen.