The O.C.
It might seem impossible now, but once upon a time, actress Shailene Woodley was recast from her role as Kaitlin Cooper on The O.C. She was replaced by Willa Holland. Shailene just wasn't a good fit, and "the version of Kaitlin Cooper that we were going to bring back to the show was a little bit older than Shailene would’ve been able to achieve on her own."