Using some of the above comments as hooks and with thanks to A. Halliwell:
"Aren't you tired, Spence, of always playing Spencer Tracy?"
---"What am I supposed to do, play Bogart?"
"After the 'Wizard of Oz' I was typecast as a lion, and there aren't all that many parts for lions."
"I was a thirteen-year-old boy for thirty years."
Clark Gable was thought of for Tarzan and Greta Garbo was asked to play Dorian Gray as a woman.
Danny Thomas would have starred in 'The Jolson Story' if he had agreed to have his nose shortened!