There's a lot about the unmade Superman Lives movie that was wild, including Michael Keaton's planned Batman cameo. Tim Burton stepped aside from superhero movies following the reception to Batman Returns, which was controversial at the time for being too dark and twisted for younger viewers. Still, in the years following this 1992 sequel, he considered directing both a Catwoman spin-off starring Michelle Pfeiffer and Superman Lives. This would have cast Nicolas Cage as the titular superhero, with the story loosely adapting "The Death of Superman" comic arc.
Burton's Superman Lives would go on to become one of the most famous unproduced blockbusters of all time. The movie spent two years in development before being canned in 1998 over rising costs, and in the aftermath, various pieces of concept art and test photos of Cage in his suit would emerge. Kevin Smith also wrote drafts for Superman Lives and told several hilirious anecdotes about his time on the project, including producer Jon Peters' bizarre insistence on having Cage's Superman fight a giant spider.
Smith later admitted in the 2015 documentary The Death of "Superman Lives": What Happened? that one big reason he wanted to write the movie was to include a scene with Batman. While George Clooney would have been the then-current Caped Crusader in the Warner Bros film franchise, it appears Burton planned on having Michael Keaton reprise Batman for Superman Lives. The actor himself confirmed his involvement to MTV (via Superman Homepage), though when asked if he was playing Batman he responded with "Not exactly." In Smith's Superman Lives draft, Batman's cameo would happen during the funeral of Superman, where he would address the grieving crowd.
Keaton's Batman Role In Superman Lives Would Have Been Great
In the Superman Lives script, the funeral would have been broadcast on a giant TV screen outside Metropolis' WGBS building. That screen would have been hijacked by Batman, who would offer his and Gotham's condolences for Superman's demise. He would also state of the fallen hero - who was killed fighting Doomsday - that "It's been said that he fought a never-ending battle for truth, justice and the American way. Honor this fallen soldier well by keeping his memory alive in the face of this adversity." The scene itself was quite brief and likely would have been something Keaton could have filmed in a couple of hours, but as Smith himself explained, fans would have gone wild for it.
Of course, Michael Keaton's Superman Lives - which would have redefined the titled character had it happened - cameo was never destined to be. Had the film gone ahead, it would have created an early shared comic book movie universe, though it's unlikely a Batman V Superman-style crossover would have occurred during this era.