Batman Begins
As one Batman Begins, another's career must end. High profile actress Katie Holmes portrayed the character of Rachel Dawes in Batman Begins, but she was recast and replaced with Maggie Gyllenhaal for the sequel. There was no bad blood on set, Katie Holmes was just tired of playing Rachel and wanted to explore other career options.
Seinfeld
Jerry’s dad, Morty Seinfeld, is one of the best parts of the show after his name. Barney Martin's performance as the father remains one of the most well-known of his career. However, the character of Morty was partially portrayed by actor Phil Bruns for the first season. He was recast because creators Jerry Seinfeld and Larry David thought the character should be grumpier and hard to please.