As today marks the 25th anniversary of the release of Tim Burton’s Batman in 1989, let us pause to remember a glitch in its unveiling courtesy of star Michael Keaton. (Hat tip to the New York Times' Dave Itzkoff for reminding us.) The day before the movie hit theaters on June 23, 1989, Keaton appeared on Late Night With David Letterman and in the course of explaining the plot of this newfangled superhero movie, he just up and gave away the movie’s big twist. (Quarter of a century old spoiler alert: The faceless mugger who killed Bruce Wayne’s parents was actually the Joker.) Jump ahead to 6:00 in the clip above for the reveal.

There are two striking things about this moment: First, it’s almost quaint how (mostly) unconcerned Keaton seems to be, especially compared to franchise stars these days who seem absolutely terrified they’re going to let any minor plot point slip. And second, there used to be a time before the Internet where a major spoiler like that could hit on TV and then have nowhere to go — no blogs, no Reddit, no YouTube. If a spoiler lands in the forest and no one’s there to Tweet it, does it make a sound?