In an interview with THR, actor Robert Wuhl reveals Batman himself, Michael Keaton, was the one to shoot the casting down.
"To put a little fly in the ointment, Michael Keaton and Michelle Pfeiffer had previously dated and broken up," . "At the time, Michael told me he was trying to get back with his ex-wife [Caroline McWilliams]. Keaton was firmly, and underline firmly, against that casting of Pfeiffer and he and Peters got into it."
Circumstances changed for the sequel and Michelle played Catwoman