Who? Classical Hollywood star.
Real? Probably not. The rumor dates from the 1930s, and the alleged film doesn’t circulate.
This story predates “tape” by decades. Call it the Joan Crawford sex flicker rumor.
The story goes: before she made it big in Hollywood, Joan Crawford shot a short pornographic film (known as “stag films” back in the day). The porn industry was very far underground at the time, so it’s unlikely that solid evidence will ever prove or disprove the story. No copies of the stag film in question are known to survive.
From a Village Voice article about celebrity sex tapes: “Ancient Hollywood gossip has it that Joan Crawford acted in several early stag films, including some with lesbian scenes.”
From a Joan Crawford fan site: “Other stories have floated around that there was a stag film with Joan called The Casting Couch. [Biographer Bob] Thomas says that both Louis B. Mayer and MGM attorney Robert Rubin viewed the film and concluded that the actress was not Joan.” This site mentions another possible rumor source: a family friend claimed that young Joan filmed a two-minute “naked dancing girl” loop for exhibition in peepshow machines.