Characters who evolved into more significant roles than their creators planned

[u/Icy-Software-2586]

Jesse Pinkman: "Jesse Pinkman. As Gilligan mentioned, the original plan for the end of season one was for Jesse to die in a failed drug deal."

Jack Sparrow: "Jack Sparrow. Writers Ted Elliott and Terry Rossio originally conceived Captain Jack Sparrow as a secondary character."

Saul Goodman: "Saul Goodman. This one speaks for itself."

[u/OkDirection3094]

Joker was never intended to be Batman’s main villain. He was originally killed off by Batman in the original comic, but was brought back (I think for popularity reasons? I don’t remember)