Michael Keaton didn’t want Michelle Pfeiffer in the first Batman because it’d be too awkward. She played Catwoman in the sequel!

The 1989 film, Batman, stars Michael Keaton in the title role, Jack Nicholson as the villain and Kim Basinger as the beautiful love interest. Just one in a long series of Batman movies, this particular Batman film was a critical and commercial success with over $400 million in box office sales.

Before this success though, the film's casting was a difficult task. A veritable who's who of Hollywood leading men were considered for the role of Batman, including Kevin Costner, Mel Gibson, Pierce Brosnan and Tom Selleck.

Producer Jon Peters and director Tim Burton both favored Michael Keaton, though. His was a controversial casting, and Warner Brothers received 50,000 protest letters about it.

Burton then suggested that Michelle Pfeiffer play Vicki Vale, the role that would later go to Bassinger.

Keaton had been in a relationship with Pfeiffer though and thought it would be too awkward. Bassinger was then cast, but Pfeiffer would later play Catwoman in "Batman Returns."

(Source)