In which films does joker appear?

Well, the 質問 is not clear at first place, c'oz "JOKER" is a character, not a person in real. The actor though {Heath Ledger} has performed in lots of movies, like my personal お気に入り "The Patriot".

The 1966 バットマン film, the 1989 バットマン film, The Dark Knight, Suicide Squad, and several animated films.