Then: Jessica Alba
Now: Kate Mara
Age: Alba was just 24 when she played Sue Storm, while Mara is 32.
Pedigree: At the time she signed on for the first movie, Alba had appeared in a number of high-profile projects, including Honey and Sin City. Mara starred on TV hits like House of Cards and American Horror Story, and she's also been on the big screen in 127 Hours and Transcendence.