In regards of Big Bang Theory if we're talking changes that don't really reflect growth but just a sudden change in direction, really only Bernadette and Amy fit. Bernadette was not introduced with her tiny firecracker personality. Nor was Amy introduced with the strong sex drive she'd later acquire out of thin air. So those two genuinely went through a change by writing mandate. And Stuart in regards to supporting characters. The others had pretty much organic growth, not counting the early season 1 episodes where an original sitcom cast typically are still being fine-tuned.