John Cassavetes’s “Opening Night” ha s long been catnip to theater fans. It’s easy to see why: The 1977 film is about an aging, hard-drinking actress, portrayed by Gena Rowlands, who becomes increasingly unhinged during a play’s out-of-town tryout.

Cassavetes shot a lot of it in front of a live audience in Pasadena, Calif., and the result constantly threads the line between fantasy and reality, performance and life.

Coincidentally, New Yorkers will be able to see two different theatrical works drawing from “Opening Night” this fall. And they are radically different from each other: The Australian import “The Second Woman” has a cast of 101 — one woman and 100 men — and runs 24 hours; a French “Opening Night” features three actors and lasts 75 minutes. (The original film has a large ensemble and goes on for two and a half hours.)

“This is an experiment: don’t expect the movie or you’ll be disappointed,” the Parisian director Cyril Teste said of his “Opening Night” — a warning that applies to both of the new shows. In comparison, Ivo van Hove’s adaptation of “Opening Night,” seen at the Brooklyn Academy of Music in 2008, feels downright conventional in retrospect, despite his reputation as an iconoclast.