Nowadays, a new superhero movie every summer seems to come around every summer, but that hasn’t always been the case.

Ultimately, when Warner Bros. announced that they were developing a big-screen adaption of Batman for release in 1989—and the hot new director Tim Burton had been signed on to direct it—comic book fans the world over were abuzz with excitement.

Unfortunately, that excitement didn’t last long. Initially, many established action stars and Hollywood A-listers were attached to play Batman, including Kevin Costner, Mel Gibson, Harrison Ford, Charlie Sheen, and Tom Selleck. Burton himself wanted to cast Pierce Brosnan, but he turned the role down claiming he didn’t want to play a comic book character. Eventually, the role went to Michael Keaton, who had recently starred in Burton’s spooky 1988 comedy, Beetlejuice. But when Keaton’s casting was announced, the prospect of having an actor who was chiefly known for his comedic roles take on the infamously gloomy Caped Crusader left a great many Batman fans feeling disappointed and angry.

Some 50,000 letters of complaint promptly arrived at Warner Bros. studios, as comic book readers around the world expressed their distaste at Keaton’s involvement. “Obviously, there was a negative response,” Burton later recalled. “I think they thought we were going to make it like the 1960s TV series, and make it campy, because they thought of Michael Keaton from Mr. Mom and Night Shift, and stuff like that.” Burton, however, had a different and decidedly darker vision in mind.

When the letters of complaint became too much to bear, producer Jon Peters took matters into his own hands and rushed together a short trailer—little more than a montage of clips, with no music—and released it to cinemas. Seeing the dark and atmospheric direction Burton had taken the story instantly silenced his critics, and anticipation started to build.

The film went on to gross more than $400 million at the box office and was followed by three sequels.