I remember alot of the names that were tossed around, rumored, and considered/tested for various parts in Batman Forever , Batman Robin , and Superman Reborn / Lives.
Batman Forever circa 1993:
Batman : Michael Keaton who walked , Kurt Russell, William Baldwin,
Robin: Marlon Wayans who was still contracted going back to Batman Returns but never really considered by Schumacer. Leonardo DiCaprio, Matt Damon, Jude Law, Ewan Macgregor, Alan Cumming
Chase Meridian: Renee Russo, Penelope Ann Miller, Robin Wright
Riddler : Robin Williams
Jack Nicholson's Joker and Tom Cruise : Jack Nicholson was rumored to appear in the finale of the film in addition to a rumor that Tom Cruise would have a guest appearance since he was visiting his then wife Nicole Kidman on the set.
Batman and Robin circa 1995
Batman : David Duchovney rumored to be considered.
Mr Freeze: Fans wanted Patrick Stewart. Sly Stallone wanted the part
Poison Ivy: Julia Roberts and Demi Moore rumored to want the part and to be considered by WB.
Batgirl: It was rumored that Julia Roberts would also be considered also for Batgirl if Demi Moore got Poison Ivy. Alyssa Milano was rumored to be a back up replacement for Alicia Silverstone if Silverstone didn't "get in shape" in time.
Catwoman: Michelle Pfeiffer was rumored to appear at the end of the film for the longest time. It basically wasn't until some of the disastrous test screening reactions were leaked online that that rumor was put to rest.
Harvey Bullock: Ernest Borgnine was rumored to play Bullock in the film for the longest time . I don't know how or why that rumor came about , but it lasted a while.
Superman Lives/Reborn
Batman : Michael Keaton was rumored to appear as Batman giving a speech addressing Superman's death.
Lois Lane: Teri Hatcher, Courtney Cox and Sandra Bullock were rumored for Lois Lane.
Steel : Shaq was rumored to reprise his role as Steel.