Modern Family
When Mitch and Cam adopted a baby on Modern Family, it made sense that they'd need a new kid for the next season. Babies grow fast, so it wasn't long before the twins who played Lilly, Ella & Jaden Hiller, were too old for the part. They were replaced by Aubrey Anderson-Emmons, who grew up on the screen. She stayed in the role from toddlerhood all the way to her teenage years.